multiple tries

backend/command/client/grpc/api.go

@@ -0,0 +1,56 @@
+package grpc
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/command"
+	"github.com/zitadel/zitadel/backend/command/query"
+	"github.com/zitadel/zitadel/backend/command/receiver"
+	"github.com/zitadel/zitadel/backend/command/receiver/cache"
+	"github.com/zitadel/zitadel/backend/storage/database"
+	"github.com/zitadel/zitadel/backend/telemetry/logging"
+	"github.com/zitadel/zitadel/backend/telemetry/tracing"
+)
+
+type api struct {
+	db database.Pool
+
+	manipulator receiver.InstanceManipulator
+	reader      receiver.InstanceReader
+	tracer      *tracing.Tracer
+	logger      *logging.Logger
+	cache       cache.Cache[receiver.InstanceIndex, string, *receiver.Instance]
+}
+
+func (a *api) CreateInstance(ctx context.Context) error {
+	instance := &receiver.Instance{
+		ID:   "123",
+		Name: "test",
+	}
+	return command.Trace(
+		a.tracer,
+		command.SetCache(a.cache,
+			command.Activity(a.logger, command.CreateInstance(a.manipulator, instance)),
+			instance,
+		),
+	).Execute(ctx)
+}
+
+func (a *api) DeleteInstance(ctx context.Context) error {
+	return command.Trace(
+		a.tracer,
+		command.DeleteCache(a.cache,
+			command.Activity(
+				a.logger,
+				command.DeleteInstance(a.manipulator, &receiver.Instance{
+					ID: "123",
+				})),
+			receiver.InstanceByID,
+			"123",
+		)).Execute(ctx)
+}
+
+func (a *api) InstanceByID(ctx context.Context) (*receiver.Instance, error) {
+	q := query.InstanceByID(a.reader, "123")
+	return q.Execute(ctx)
+}

backend/command/command/caching.go

@@ -0,0 +1,102 @@
+package command
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/receiver/cache"
+)
+
+type setCache[I, K comparable, V cache.Entry[I, K]] struct {
+	cache   cache.Cache[I, K, V]
+	command Command
+	entry   V
+}
+
+// SetCache decorates the command, if the command is executed without error it will set the cache entry.
+func SetCache[I, K comparable, V cache.Entry[I, K]](cache cache.Cache[I, K, V], command Command, entry V) Command {
+	return &setCache[I, K, V]{
+		cache:   cache,
+		command: command,
+		entry:   entry,
+	}
+}
+
+var _ Command = (*setCache[any, any, cache.Entry[any, any]])(nil)
+
+// Execute implements [Command].
+func (s *setCache[I, K, V]) Execute(ctx context.Context) error {
+	if err := s.command.Execute(ctx); err != nil {
+		return err
+	}
+	s.cache.Set(ctx, s.entry)
+	return nil
+}
+
+// Name implements [Command].
+func (s *setCache[I, K, V]) Name() string {
+	return s.command.Name()
+}
+
+type deleteCache[I, K comparable, V cache.Entry[I, K]] struct {
+	cache   cache.Cache[I, K, V]
+	command Command
+	index   I
+	keys    []K
+}
+
+// DeleteCache decorates the command, if the command is executed without error it will delete the cache entry.
+func DeleteCache[I, K comparable, V cache.Entry[I, K]](cache cache.Cache[I, K, V], command Command, index I, keys ...K) Command {
+	return &deleteCache[I, K, V]{
+		cache:   cache,
+		command: command,
+		index:   index,
+		keys:    keys,
+	}
+}
+
+var _ Command = (*deleteCache[any, any, cache.Entry[any, any]])(nil)
+
+// Execute implements [Command].
+func (s *deleteCache[I, K, V]) Execute(ctx context.Context) error {
+	if err := s.command.Execute(ctx); err != nil {
+		return err
+	}
+	return s.cache.Delete(ctx, s.index, s.keys...)
+}
+
+// Name implements [Command].
+func (s *deleteCache[I, K, V]) Name() string {
+	return s.command.Name()
+}
+
+type invalidateCache[I, K comparable, V cache.Entry[I, K]] struct {
+	cache   cache.Cache[I, K, V]
+	command Command
+	index   I
+	keys    []K
+}
+
+// InvalidateCache decorates the command, if the command is executed without error it will invalidate the cache entry.
+func InvalidateCache[I, K comparable, V cache.Entry[I, K]](cache cache.Cache[I, K, V], command Command, index I, keys ...K) Command {
+	return &invalidateCache[I, K, V]{
+		cache:   cache,
+		command: command,
+		index:   index,
+		keys:    keys,
+	}
+}
+
+var _ Command = (*invalidateCache[any, any, cache.Entry[any, any]])(nil)
+
+// Execute implements [Command].
+func (s *invalidateCache[I, K, V]) Execute(ctx context.Context) error {
+	if err := s.command.Execute(ctx); err != nil {
+		return err
+	}
+	return s.cache.Invalidate(ctx, s.index, s.keys...)
+}
+
+// Name implements [Command].
+func (s *invalidateCache[I, K, V]) Name() string {
+	return s.command.Name()
+}

backend/command/command/command.go

@@ -1,6 +1,10 @@
 package command
 
-import "context"
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/receiver/cache"
+)
 
 type Command interface {
 	Execute(context.Context) error
@@ -20,3 +24,8 @@ func (b *Batch) Execute(ctx context.Context) error {
 	}
 	return nil
 }
+
+type CacheableCommand[I, K comparable, V cache.Entry[I, K]] interface {
+	Command
+	Entry() V
+}

backend/command/command/instance.go

@@ -65,7 +65,7 @@ func UpdateInstance(receiver receiver.InstanceManipulator, instance *receiver.In
 
 func (u *updateInstance) Execute(ctx context.Context) error {
 	u.Instance.Name = u.name
-	// return u.receiver.(ctx, u.Instance)
+	// return u.receiver.Update(ctx, u.Instance)
 	return nil
 }
 

backend/command/command/logging.go

@@ -8,21 +8,28 @@ import (
 	"github.com/zitadel/zitadel/backend/telemetry/logging"
 )
 
-type Logger struct {
+type logger struct {
 	level slog.Level
 	*logging.Logger
 	cmd Command
 }
 
-func Activity(l *logging.Logger, command Command) *Logger {
-	return &Logger{
+// Activity decorates the commands execute method with logging.
+// It logs the command name, duration, and success or failure of the command.
+func Activity(l *logging.Logger, command Command) Command {
+	return &logger{
 		Logger: l.With(slog.String("type", "activity")),
 		level:  slog.LevelInfo,
 		cmd:    command,
 	}
 }
 
-func (l *Logger) Execute(ctx context.Context) error {
+// Name implements [Command].
+func (l *logger) Name() string {
+	return l.cmd.Name()
+}
+
+func (l *logger) Execute(ctx context.Context) error {
 	start := time.Now()
 	log := l.Logger.With(slog.String("command", l.cmd.Name()))
 	log.InfoContext(ctx, "execute")

backend/command/command/tracing.go

@@ -6,12 +6,27 @@ import (
 	"github.com/zitadel/zitadel/backend/telemetry/tracing"
 )
 
-type Trace struct {
+type trace struct {
 	command Command
 	tracer  *tracing.Tracer
 }
 
-func (t *Trace) Execute(ctx context.Context) error {
+// Trace decorates the commands execute method with tracing.
+// It creates a span with the command name and records any errors that occur during execution.
+// The span is ended after the command is executed.
+func Trace(tracer *tracing.Tracer, command Command) Command {
+	return &trace{
+		command: command,
+		tracer:  tracer,
+	}
+}
+
+// Name implements [Command].
+func (l *trace) Name() string {
+	return l.command.Name()
+}
+
+func (t *trace) Execute(ctx context.Context) error {
 	ctx, span := t.tracer.Start(ctx, t.command.Name())
 	defer span.End()
 	err := t.command.Execute(ctx)

backend/command/invoker/api.go

@@ -1,38 +0,0 @@
-package invoker
-
-import (
-	"context"
-
-	"github.com/zitadel/zitadel/backend/command/command"
-	"github.com/zitadel/zitadel/backend/command/query"
-	"github.com/zitadel/zitadel/backend/command/receiver"
-	"github.com/zitadel/zitadel/backend/command/receiver/db"
-	"github.com/zitadel/zitadel/backend/storage/database"
-)
-
-type api struct {
-	db database.Pool
-
-	manipulator receiver.InstanceManipulator
-	reader      receiver.InstanceReader
-}
-
-func (a *api) CreateInstance(ctx context.Context) error {
-	cmd := command.CreateInstance(db.NewInstance(a.db), &receiver.Instance{
-		ID:   "123",
-		Name: "test",
-	})
-	return cmd.Execute(ctx)
-}
-
-func (a *api) DeleteInstance(ctx context.Context) error {
-	cmd := command.DeleteInstance(db.NewInstance(a.db), &receiver.Instance{
-		ID: "123",
-	})
-	return cmd.Execute(ctx)
-}
-
-func (a *api) InstanceByID(ctx context.Context) (*receiver.Instance, error) {
-	q := query.InstanceByID(a.reader, "123")
-	return q.Execute(ctx)
-}

backend/command/receiver/cache/cache.go

@@ -0,0 +1,112 @@
+// Package cache provides abstraction of cache implementations that can be used by zitadel.
+package cache
+
+import (
+	"context"
+	"time"
+
+	"github.com/zitadel/logging"
+)
+
+// Purpose describes which object types are stored by a cache.
+type Purpose int
+
+//go:generate enumer -type Purpose -transform snake -trimprefix Purpose
+const (
+	PurposeUnspecified Purpose = iota
+	PurposeAuthzInstance
+	PurposeMilestones
+	PurposeOrganization
+	PurposeIdPFormCallback
+)
+
+// Cache stores objects with a value of type `V`.
+// Objects may be referred to by one or more indices.
+// Implementations may encode the value for storage.
+// This means non-exported fields may be lost and objects
+// with function values may fail to encode.
+// See https://pkg.go.dev/encoding/json#Marshal for example.
+//
+// `I` is the type by which indices are identified,
+// typically an enum for type-safe access.
+// Indices are defined when calling the constructor of an implementation of this interface.
+// It is illegal to refer to an idex not defined during construction.
+//
+// `K` is the type used as key in each index.
+// Due to the limitations in type constraints, all indices use the same key type.
+//
+// Implementations are free to use stricter type constraints or fixed typing.
+type Cache[I, K comparable, V Entry[I, K]] interface {
+	// Get an object through specified index.
+	// An [IndexUnknownError] may be returned if the index is unknown.
+	// [ErrCacheMiss] is returned if the key was not found in the index,
+	// or the object is not valid.
+	Get(ctx context.Context, index I, key K) (V, bool)
+
+	// Set an object.
+	// Keys are created on each index based in the [Entry.Keys] method.
+	// If any key maps to an existing object, the object is invalidated,
+	// regardless if the object has other keys defined in the new entry.
+	// This to prevent ghost objects when an entry reduces the amount of keys
+	// for a given index.
+	Set(ctx context.Context, value V)
+
+	// Invalidate an object through specified index.
+	// Implementations may choose to instantly delete the object,
+	// defer until prune or a separate cleanup routine.
+	// Invalidated object are no longer returned from Get.
+	// It is safe to call Invalidate multiple times or on non-existing entries.
+	Invalidate(ctx context.Context, index I, key ...K) error
+
+	// Delete one or more keys from a specific index.
+	// An [IndexUnknownError] may be returned if the index is unknown.
+	// The referred object is not invalidated and may still be accessible though
+	// other indices and keys.
+	// It is safe to call Delete multiple times or on non-existing entries
+	Delete(ctx context.Context, index I, key ...K) error
+
+	// Truncate deletes all cached objects.
+	Truncate(ctx context.Context) error
+}
+
+// Entry contains a value of type `V` to be cached.
+//
+// `I` is the type by which indices are identified,
+// typically an enum for type-safe access.
+//
+// `K` is the type used as key in an index.
+// Due to the limitations in type constraints, all indices use the same key type.
+type Entry[I, K comparable] interface {
+	// Keys returns which keys map to the object in a specified index.
+	// May return nil if the index in unknown or when there are no keys.
+	Keys(index I) (key []K)
+}
+
+type Connector int
+
+//go:generate enumer -type Connector -transform snake -trimprefix Connector -linecomment -text
+const (
+	// Empty line comment ensures empty string for unspecified value
+	ConnectorUnspecified Connector = iota //
+	ConnectorMemory
+	ConnectorPostgres
+	ConnectorRedis
+)
+
+type Config struct {
+	Connector Connector
+
+	// Age since an object was added to the cache,
+	// after which the object is considered invalid.
+	// 0 disables max age checks.
+	MaxAge time.Duration
+
+	// Age since last use (Get) of an object,
+	// after which the object is considered invalid.
+	// 0 disables last use age checks.
+	LastUseAge time.Duration
+
+	// Log allows logging of the specific cache.
+	// By default only errors are logged to stdout.
+	Log *logging.Config
+}

backend/command/receiver/cache/connector/connector.go

@@ -0,0 +1,49 @@
+// Package connector provides glue between the [cache.Cache] interface and implementations from the connector sub-packages.
+package connector
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/zitadel/zitadel/backend/storage/cache"
+	"github.com/zitadel/zitadel/backend/storage/cache/connector/gomap"
+	"github.com/zitadel/zitadel/backend/storage/cache/connector/noop"
+)
+
+type CachesConfig struct {
+	Connectors struct {
+		Memory gomap.Config
+	}
+	Instance         *cache.Config
+	Milestones       *cache.Config
+	Organization     *cache.Config
+	IdPFormCallbacks *cache.Config
+}
+
+type Connectors struct {
+	Config CachesConfig
+	Memory *gomap.Connector
+}
+
+func StartConnectors(conf *CachesConfig) (Connectors, error) {
+	if conf == nil {
+		return Connectors{}, nil
+	}
+	return Connectors{
+		Config: *conf,
+		Memory: gomap.NewConnector(conf.Connectors.Memory),
+	}, nil
+}
+
+func StartCache[I ~int, K ~string, V cache.Entry[I, K]](background context.Context, indices []I, purpose cache.Purpose, conf *cache.Config, connectors Connectors) (cache.Cache[I, K, V], error) {
+	if conf == nil || conf.Connector == cache.ConnectorUnspecified {
+		return noop.NewCache[I, K, V](), nil
+	}
+	if conf.Connector == cache.ConnectorMemory && connectors.Memory != nil {
+		c := gomap.NewCache[I, K, V](background, indices, *conf)
+		connectors.Memory.Config.StartAutoPrune(background, c, purpose)
+		return c, nil
+	}
+
+	return nil, fmt.Errorf("cache connector %q not enabled", conf.Connector)
+}

backend/command/receiver/cache/connector/gomap/connector.go

@@ -0,0 +1,23 @@
+package gomap
+
+import (
+	"github.com/zitadel/zitadel/backend/storage/cache"
+)
+
+type Config struct {
+	Enabled   bool
+	AutoPrune cache.AutoPruneConfig
+}
+
+type Connector struct {
+	Config cache.AutoPruneConfig
+}
+
+func NewConnector(config Config) *Connector {
+	if !config.Enabled {
+		return nil
+	}
+	return &Connector{
+		Config: config.AutoPrune,
+	}
+}

backend/command/receiver/cache/connector/gomap/gomap.go

@@ -0,0 +1,200 @@
+package gomap
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+	"maps"
+	"os"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/zitadel/zitadel/backend/storage/cache"
+)
+
+type mapCache[I, K comparable, V cache.Entry[I, K]] struct {
+	config   *cache.Config
+	indexMap map[I]*index[K, V]
+	logger   *slog.Logger
+}
+
+// NewCache returns an in-memory Cache implementation based on the builtin go map type.
+// Object values are stored as-is and there is no encoding or decoding involved.
+func NewCache[I, K comparable, V cache.Entry[I, K]](background context.Context, indices []I, config cache.Config) cache.PrunerCache[I, K, V] {
+	m := &mapCache[I, K, V]{
+		config:   &config,
+		indexMap: make(map[I]*index[K, V], len(indices)),
+		logger: slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{
+			AddSource: true,
+			Level:     slog.LevelError,
+		})),
+	}
+	if config.Log != nil {
+		m.logger = config.Log.Slog()
+	}
+	m.logger.InfoContext(background, "map cache logging enabled")
+
+	for _, name := range indices {
+		m.indexMap[name] = &index[K, V]{
+			config:  m.config,
+			entries: make(map[K]*entry[V]),
+		}
+	}
+	return m
+}
+
+func (c *mapCache[I, K, V]) Get(ctx context.Context, index I, key K) (value V, ok bool) {
+	i, ok := c.indexMap[index]
+	if !ok {
+		c.logger.ErrorContext(ctx, "map cache get", "err", cache.NewIndexUnknownErr(index), "index", index, "key", key)
+		return value, false
+	}
+	entry, err := i.Get(key)
+	if err == nil {
+		c.logger.DebugContext(ctx, "map cache get", "index", index, "key", key)
+		return entry.value, true
+	}
+	if errors.Is(err, cache.ErrCacheMiss) {
+		c.logger.InfoContext(ctx, "map cache get", "err", err, "index", index, "key", key)
+		return value, false
+	}
+	c.logger.ErrorContext(ctx, "map cache get", "err", cache.NewIndexUnknownErr(index), "index", index, "key", key)
+	return value, false
+}
+
+func (c *mapCache[I, K, V]) Set(ctx context.Context, value V) {
+	now := time.Now()
+	entry := &entry[V]{
+		value:   value,
+		created: now,
+	}
+	entry.lastUse.Store(now.UnixMicro())
+
+	for name, i := range c.indexMap {
+		keys := value.Keys(name)
+		i.Set(keys, entry)
+		c.logger.DebugContext(ctx, "map cache set", "index", name, "keys", keys)
+	}
+}
+
+func (c *mapCache[I, K, V]) Invalidate(ctx context.Context, index I, keys ...K) error {
+	i, ok := c.indexMap[index]
+	if !ok {
+		return cache.NewIndexUnknownErr(index)
+	}
+	i.Invalidate(keys)
+	c.logger.DebugContext(ctx, "map cache invalidate", "index", index, "keys", keys)
+	return nil
+}
+
+func (c *mapCache[I, K, V]) Delete(ctx context.Context, index I, keys ...K) error {
+	i, ok := c.indexMap[index]
+	if !ok {
+		return cache.NewIndexUnknownErr(index)
+	}
+	i.Delete(keys)
+	c.logger.DebugContext(ctx, "map cache delete", "index", index, "keys", keys)
+	return nil
+}
+
+func (c *mapCache[I, K, V]) Prune(ctx context.Context) error {
+	for name, index := range c.indexMap {
+		index.Prune()
+		c.logger.DebugContext(ctx, "map cache prune", "index", name)
+	}
+	return nil
+}
+
+func (c *mapCache[I, K, V]) Truncate(ctx context.Context) error {
+	for name, index := range c.indexMap {
+		index.Truncate()
+		c.logger.DebugContext(ctx, "map cache truncate", "index", name)
+	}
+	return nil
+}
+
+type index[K comparable, V any] struct {
+	mutex   sync.RWMutex
+	config  *cache.Config
+	entries map[K]*entry[V]
+}
+
+func (i *index[K, V]) Get(key K) (*entry[V], error) {
+	i.mutex.RLock()
+	entry, ok := i.entries[key]
+	i.mutex.RUnlock()
+	if ok && entry.isValid(i.config) {
+		return entry, nil
+	}
+	return nil, cache.ErrCacheMiss
+}
+
+func (c *index[K, V]) Set(keys []K, entry *entry[V]) {
+	c.mutex.Lock()
+	for _, key := range keys {
+		c.entries[key] = entry
+	}
+	c.mutex.Unlock()
+}
+
+func (i *index[K, V]) Invalidate(keys []K) {
+	i.mutex.RLock()
+	for _, key := range keys {
+		if entry, ok := i.entries[key]; ok {
+			entry.invalid.Store(true)
+		}
+	}
+	i.mutex.RUnlock()
+}
+
+func (c *index[K, V]) Delete(keys []K) {
+	c.mutex.Lock()
+	for _, key := range keys {
+		delete(c.entries, key)
+	}
+	c.mutex.Unlock()
+}
+
+func (c *index[K, V]) Prune() {
+	c.mutex.Lock()
+	maps.DeleteFunc(c.entries, func(_ K, entry *entry[V]) bool {
+		return !entry.isValid(c.config)
+	})
+	c.mutex.Unlock()
+}
+
+func (c *index[K, V]) Truncate() {
+	c.mutex.Lock()
+	c.entries = make(map[K]*entry[V])
+	c.mutex.Unlock()
+}
+
+type entry[V any] struct {
+	value   V
+	created time.Time
+	invalid atomic.Bool
+	lastUse atomic.Int64 // UnixMicro time
+}
+
+func (e *entry[V]) isValid(c *cache.Config) bool {
+	if e.invalid.Load() {
+		return false
+	}
+	now := time.Now()
+	if c.MaxAge > 0 {
+		if e.created.Add(c.MaxAge).Before(now) {
+			e.invalid.Store(true)
+			return false
+		}
+	}
+	if c.LastUseAge > 0 {
+		lastUse := e.lastUse.Load()
+		if time.UnixMicro(lastUse).Add(c.LastUseAge).Before(now) {
+			e.invalid.Store(true)
+			return false
+		}
+		e.lastUse.CompareAndSwap(lastUse, now.UnixMicro())
+	}
+	return true
+}

backend/command/receiver/cache/connector/gomap/gomap_test.go

@@ -0,0 +1,329 @@
+package gomap
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/zitadel/logging"
+
+	"github.com/zitadel/zitadel/backend/storage/cache"
+)
+
+type testIndex int
+
+const (
+	testIndexID testIndex = iota
+	testIndexName
+)
+
+var testIndices = []testIndex{
+	testIndexID,
+	testIndexName,
+}
+
+type testObject struct {
+	id    string
+	names []string
+}
+
+func (o *testObject) Keys(index testIndex) []string {
+	switch index {
+	case testIndexID:
+		return []string{o.id}
+	case testIndexName:
+		return o.names
+	default:
+		return nil
+	}
+}
+
+func Test_mapCache_Get(t *testing.T) {
+	c := NewCache[testIndex, string, *testObject](context.Background(), testIndices, cache.Config{
+		MaxAge:     time.Second,
+		LastUseAge: time.Second / 4,
+		Log: &logging.Config{
+			Level:     "debug",
+			AddSource: true,
+		},
+	})
+	obj := &testObject{
+		id:    "id",
+		names: []string{"foo", "bar"},
+	}
+	c.Set(context.Background(), obj)
+
+	type args struct {
+		index testIndex
+		key   string
+	}
+	tests := []struct {
+		name   string
+		args   args
+		want   *testObject
+		wantOk bool
+	}{
+		{
+			name: "ok",
+			args: args{
+				index: testIndexID,
+				key:   "id",
+			},
+			want:   obj,
+			wantOk: true,
+		},
+		{
+			name: "miss",
+			args: args{
+				index: testIndexID,
+				key:   "spanac",
+			},
+			want:   nil,
+			wantOk: false,
+		},
+		{
+			name: "unknown index",
+			args: args{
+				index: 99,
+				key:   "id",
+			},
+			want:   nil,
+			wantOk: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, ok := c.Get(context.Background(), tt.args.index, tt.args.key)
+			assert.Equal(t, tt.want, got)
+			assert.Equal(t, tt.wantOk, ok)
+		})
+	}
+}
+
+func Test_mapCache_Invalidate(t *testing.T) {
+	c := NewCache[testIndex, string, *testObject](context.Background(), testIndices, cache.Config{
+		MaxAge:     time.Second,
+		LastUseAge: time.Second / 4,
+		Log: &logging.Config{
+			Level:     "debug",
+			AddSource: true,
+		},
+	})
+	obj := &testObject{
+		id:    "id",
+		names: []string{"foo", "bar"},
+	}
+	c.Set(context.Background(), obj)
+	err := c.Invalidate(context.Background(), testIndexName, "bar")
+	require.NoError(t, err)
+	got, ok := c.Get(context.Background(), testIndexID, "id")
+	assert.Nil(t, got)
+	assert.False(t, ok)
+}
+
+func Test_mapCache_Delete(t *testing.T) {
+	c := NewCache[testIndex, string, *testObject](context.Background(), testIndices, cache.Config{
+		MaxAge:     time.Second,
+		LastUseAge: time.Second / 4,
+		Log: &logging.Config{
+			Level:     "debug",
+			AddSource: true,
+		},
+	})
+	obj := &testObject{
+		id:    "id",
+		names: []string{"foo", "bar"},
+	}
+	c.Set(context.Background(), obj)
+	err := c.Delete(context.Background(), testIndexName, "bar")
+	require.NoError(t, err)
+
+	// Shouldn't find object by deleted name
+	got, ok := c.Get(context.Background(), testIndexName, "bar")
+	assert.Nil(t, got)
+	assert.False(t, ok)
+
+	// Should find object by other name
+	got, ok = c.Get(context.Background(), testIndexName, "foo")
+	assert.Equal(t, obj, got)
+	assert.True(t, ok)
+
+	// Should find object by id
+	got, ok = c.Get(context.Background(), testIndexID, "id")
+	assert.Equal(t, obj, got)
+	assert.True(t, ok)
+}
+
+func Test_mapCache_Prune(t *testing.T) {
+	c := NewCache[testIndex, string, *testObject](context.Background(), testIndices, cache.Config{
+		MaxAge:     time.Second,
+		LastUseAge: time.Second / 4,
+		Log: &logging.Config{
+			Level:     "debug",
+			AddSource: true,
+		},
+	})
+
+	objects := []*testObject{
+		{
+			id:    "id1",
+			names: []string{"foo", "bar"},
+		},
+		{
+			id:    "id2",
+			names: []string{"hello"},
+		},
+	}
+	for _, obj := range objects {
+		c.Set(context.Background(), obj)
+	}
+	// invalidate one entry
+	err := c.Invalidate(context.Background(), testIndexName, "bar")
+	require.NoError(t, err)
+
+	err = c.(cache.Pruner).Prune(context.Background())
+	require.NoError(t, err)
+
+	// Other object should still be found
+	got, ok := c.Get(context.Background(), testIndexID, "id2")
+	assert.Equal(t, objects[1], got)
+	assert.True(t, ok)
+}
+
+func Test_mapCache_Truncate(t *testing.T) {
+	c := NewCache[testIndex, string, *testObject](context.Background(), testIndices, cache.Config{
+		MaxAge:     time.Second,
+		LastUseAge: time.Second / 4,
+		Log: &logging.Config{
+			Level:     "debug",
+			AddSource: true,
+		},
+	})
+	objects := []*testObject{
+		{
+			id:    "id1",
+			names: []string{"foo", "bar"},
+		},
+		{
+			id:    "id2",
+			names: []string{"hello"},
+		},
+	}
+	for _, obj := range objects {
+		c.Set(context.Background(), obj)
+	}
+
+	err := c.Truncate(context.Background())
+	require.NoError(t, err)
+
+	mc := c.(*mapCache[testIndex, string, *testObject])
+	for _, index := range mc.indexMap {
+		index.mutex.RLock()
+		assert.Len(t, index.entries, 0)
+		index.mutex.RUnlock()
+	}
+}
+
+func Test_entry_isValid(t *testing.T) {
+	type fields struct {
+		created time.Time
+		invalid bool
+		lastUse time.Time
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		config *cache.Config
+		want   bool
+	}{
+		{
+			name: "invalid",
+			fields: fields{
+				created: time.Now(),
+				invalid: true,
+				lastUse: time.Now(),
+			},
+			config: &cache.Config{
+				MaxAge:     time.Minute,
+				LastUseAge: time.Second,
+			},
+			want: false,
+		},
+		{
+			name: "max age exceeded",
+			fields: fields{
+				created: time.Now().Add(-(time.Minute + time.Second)),
+				invalid: false,
+				lastUse: time.Now(),
+			},
+			config: &cache.Config{
+				MaxAge:     time.Minute,
+				LastUseAge: time.Second,
+			},
+			want: false,
+		},
+		{
+			name: "max age disabled",
+			fields: fields{
+				created: time.Now().Add(-(time.Minute + time.Second)),
+				invalid: false,
+				lastUse: time.Now(),
+			},
+			config: &cache.Config{
+				LastUseAge: time.Second,
+			},
+			want: true,
+		},
+		{
+			name: "last use age exceeded",
+			fields: fields{
+				created: time.Now().Add(-(time.Minute / 2)),
+				invalid: false,
+				lastUse: time.Now().Add(-(time.Second * 2)),
+			},
+			config: &cache.Config{
+				MaxAge:     time.Minute,
+				LastUseAge: time.Second,
+			},
+			want: false,
+		},
+		{
+			name: "last use age disabled",
+			fields: fields{
+				created: time.Now().Add(-(time.Minute / 2)),
+				invalid: false,
+				lastUse: time.Now().Add(-(time.Second * 2)),
+			},
+			config: &cache.Config{
+				MaxAge: time.Minute,
+			},
+			want: true,
+		},
+		{
+			name: "valid",
+			fields: fields{
+				created: time.Now(),
+				invalid: false,
+				lastUse: time.Now(),
+			},
+			config: &cache.Config{
+				MaxAge:     time.Minute,
+				LastUseAge: time.Second,
+			},
+			want: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			e := &entry[any]{
+				created: tt.fields.created,
+			}
+			e.invalid.Store(tt.fields.invalid)
+			e.lastUse.Store(tt.fields.lastUse.UnixMicro())
+			got := e.isValid(tt.config)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}

backend/command/receiver/cache/connector/noop/noop.go

@@ -0,0 +1,21 @@
+package noop
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/storage/cache"
+)
+
+type noop[I, K comparable, V cache.Entry[I, K]] struct{}
+
+// NewCache returns a cache that does nothing
+func NewCache[I, K comparable, V cache.Entry[I, K]]() cache.Cache[I, K, V] {
+	return noop[I, K, V]{}
+}
+
+func (noop[I, K, V]) Set(context.Context, V)                          {}
+func (noop[I, K, V]) Get(context.Context, I, K) (value V, ok bool)    { return }
+func (noop[I, K, V]) Invalidate(context.Context, I, ...K) (err error) { return }
+func (noop[I, K, V]) Delete(context.Context, I, ...K) (err error)     { return }
+func (noop[I, K, V]) Prune(context.Context) (err error)               { return }
+func (noop[I, K, V]) Truncate(context.Context) (err error)            { return }

backend/command/receiver/cache/connector_enumer.go

@@ -0,0 +1,98 @@
+// Code generated by "enumer -type Connector -transform snake -trimprefix Connector -linecomment -text"; DO NOT EDIT.
+
+package cache
+
+import (
+	"fmt"
+	"strings"
+)
+
+const _ConnectorName = "memorypostgresredis"
+
+var _ConnectorIndex = [...]uint8{0, 0, 6, 14, 19}
+
+const _ConnectorLowerName = "memorypostgresredis"
+
+func (i Connector) String() string {
+	if i < 0 || i >= Connector(len(_ConnectorIndex)-1) {
+		return fmt.Sprintf("Connector(%d)", i)
+	}
+	return _ConnectorName[_ConnectorIndex[i]:_ConnectorIndex[i+1]]
+}
+
+// An "invalid array index" compiler error signifies that the constant values have changed.
+// Re-run the stringer command to generate them again.
+func _ConnectorNoOp() {
+	var x [1]struct{}
+	_ = x[ConnectorUnspecified-(0)]
+	_ = x[ConnectorMemory-(1)]
+	_ = x[ConnectorPostgres-(2)]
+	_ = x[ConnectorRedis-(3)]
+}
+
+var _ConnectorValues = []Connector{ConnectorUnspecified, ConnectorMemory, ConnectorPostgres, ConnectorRedis}
+
+var _ConnectorNameToValueMap = map[string]Connector{
+	_ConnectorName[0:0]:        ConnectorUnspecified,
+	_ConnectorLowerName[0:0]:   ConnectorUnspecified,
+	_ConnectorName[0:6]:        ConnectorMemory,
+	_ConnectorLowerName[0:6]:   ConnectorMemory,
+	_ConnectorName[6:14]:       ConnectorPostgres,
+	_ConnectorLowerName[6:14]:  ConnectorPostgres,
+	_ConnectorName[14:19]:      ConnectorRedis,
+	_ConnectorLowerName[14:19]: ConnectorRedis,
+}
+
+var _ConnectorNames = []string{
+	_ConnectorName[0:0],
+	_ConnectorName[0:6],
+	_ConnectorName[6:14],
+	_ConnectorName[14:19],
+}
+
+// ConnectorString retrieves an enum value from the enum constants string name.
+// Throws an error if the param is not part of the enum.
+func ConnectorString(s string) (Connector, error) {
+	if val, ok := _ConnectorNameToValueMap[s]; ok {
+		return val, nil
+	}
+
+	if val, ok := _ConnectorNameToValueMap[strings.ToLower(s)]; ok {
+		return val, nil
+	}
+	return 0, fmt.Errorf("%s does not belong to Connector values", s)
+}
+
+// ConnectorValues returns all values of the enum
+func ConnectorValues() []Connector {
+	return _ConnectorValues
+}
+
+// ConnectorStrings returns a slice of all String values of the enum
+func ConnectorStrings() []string {
+	strs := make([]string, len(_ConnectorNames))
+	copy(strs, _ConnectorNames)
+	return strs
+}
+
+// IsAConnector returns "true" if the value is listed in the enum definition. "false" otherwise
+func (i Connector) IsAConnector() bool {
+	for _, v := range _ConnectorValues {
+		if i == v {
+			return true
+		}
+	}
+	return false
+}
+
+// MarshalText implements the encoding.TextMarshaler interface for Connector
+func (i Connector) MarshalText() ([]byte, error) {
+	return []byte(i.String()), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface for Connector
+func (i *Connector) UnmarshalText(text []byte) error {
+	var err error
+	*i, err = ConnectorString(string(text))
+	return err
+}

backend/command/receiver/cache/error.go

@@ -0,0 +1,29 @@
+package cache
+
+import (
+	"errors"
+	"fmt"
+)
+
+type IndexUnknownError[I comparable] struct {
+	index I
+}
+
+func NewIndexUnknownErr[I comparable](index I) error {
+	return IndexUnknownError[I]{index}
+}
+
+func (i IndexUnknownError[I]) Error() string {
+	return fmt.Sprintf("index %v unknown", i.index)
+}
+
+func (a IndexUnknownError[I]) Is(err error) bool {
+	if b, ok := err.(IndexUnknownError[I]); ok {
+		return a.index == b.index
+	}
+	return false
+}
+
+var (
+	ErrCacheMiss = errors.New("cache miss")
+)

backend/command/receiver/cache/pruner.go

@@ -0,0 +1,76 @@
+package cache
+
+import (
+	"context"
+	"math/rand"
+	"time"
+
+	"github.com/jonboulle/clockwork"
+	"github.com/zitadel/logging"
+)
+
+// Pruner is an optional [Cache] interface.
+type Pruner interface {
+	// Prune deletes all invalidated or expired objects.
+	Prune(ctx context.Context) error
+}
+
+type PrunerCache[I, K comparable, V Entry[I, K]] interface {
+	Cache[I, K, V]
+	Pruner
+}
+
+type AutoPruneConfig struct {
+	// Interval at which the cache is automatically pruned.
+	// 0 or lower disables automatic pruning.
+	Interval time.Duration
+
+	// Timeout for an automatic prune.
+	// It is recommended to keep the value shorter than AutoPruneInterval
+	// 0 or lower disables automatic pruning.
+	Timeout time.Duration
+}
+
+func (c AutoPruneConfig) StartAutoPrune(background context.Context, pruner Pruner, purpose Purpose) (close func()) {
+	return c.startAutoPrune(background, pruner, purpose, clockwork.NewRealClock())
+}
+
+func (c *AutoPruneConfig) startAutoPrune(background context.Context, pruner Pruner, purpose Purpose, clock clockwork.Clock) (close func()) {
+	if c.Interval <= 0 {
+		return func() {}
+	}
+	background, cancel := context.WithCancel(background)
+	// randomize the first interval
+	timer := clock.NewTimer(time.Duration(rand.Int63n(int64(c.Interval))))
+	go c.pruneTimer(background, pruner, purpose, timer)
+	return cancel
+}
+
+func (c *AutoPruneConfig) pruneTimer(background context.Context, pruner Pruner, purpose Purpose, timer clockwork.Timer) {
+	defer func() {
+		if !timer.Stop() {
+			<-timer.Chan()
+		}
+	}()
+
+	for {
+		select {
+		case <-background.Done():
+			return
+		case <-timer.Chan():
+			err := c.doPrune(background, pruner)
+			logging.OnError(err).WithField("purpose", purpose).Error("cache auto prune")
+			timer.Reset(c.Interval)
+		}
+	}
+}
+
+func (c *AutoPruneConfig) doPrune(background context.Context, pruner Pruner) error {
+	ctx, cancel := context.WithCancel(background)
+	defer cancel()
+	if c.Timeout > 0 {
+		ctx, cancel = context.WithTimeout(background, c.Timeout)
+		defer cancel()
+	}
+	return pruner.Prune(ctx)
+}

backend/command/receiver/cache/pruner_test.go

@@ -0,0 +1,43 @@
+package cache
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/jonboulle/clockwork"
+	"github.com/stretchr/testify/assert"
+)
+
+type testPruner struct {
+	called chan struct{}
+}
+
+func (p *testPruner) Prune(context.Context) error {
+	p.called <- struct{}{}
+	return nil
+}
+
+func TestAutoPruneConfig_startAutoPrune(t *testing.T) {
+	c := AutoPruneConfig{
+		Interval: time.Second,
+		Timeout:  time.Millisecond,
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	pruner := testPruner{
+		called: make(chan struct{}),
+	}
+	clock := clockwork.NewFakeClock()
+	close := c.startAutoPrune(ctx, &pruner, PurposeAuthzInstance, clock)
+	defer close()
+	clock.Advance(time.Second)
+
+	select {
+	case _, ok := <-pruner.called:
+		assert.True(t, ok)
+	case <-ctx.Done():
+		t.Fatal(ctx.Err())
+	}
+}

backend/command/receiver/cache/purpose_enumer.go

@@ -0,0 +1,90 @@
+// Code generated by "enumer -type Purpose -transform snake -trimprefix Purpose"; DO NOT EDIT.
+
+package cache
+
+import (
+	"fmt"
+	"strings"
+)
+
+const _PurposeName = "unspecifiedauthz_instancemilestonesorganizationid_p_form_callback"
+
+var _PurposeIndex = [...]uint8{0, 11, 25, 35, 47, 65}
+
+const _PurposeLowerName = "unspecifiedauthz_instancemilestonesorganizationid_p_form_callback"
+
+func (i Purpose) String() string {
+	if i < 0 || i >= Purpose(len(_PurposeIndex)-1) {
+		return fmt.Sprintf("Purpose(%d)", i)
+	}
+	return _PurposeName[_PurposeIndex[i]:_PurposeIndex[i+1]]
+}
+
+// An "invalid array index" compiler error signifies that the constant values have changed.
+// Re-run the stringer command to generate them again.
+func _PurposeNoOp() {
+	var x [1]struct{}
+	_ = x[PurposeUnspecified-(0)]
+	_ = x[PurposeAuthzInstance-(1)]
+	_ = x[PurposeMilestones-(2)]
+	_ = x[PurposeOrganization-(3)]
+	_ = x[PurposeIdPFormCallback-(4)]
+}
+
+var _PurposeValues = []Purpose{PurposeUnspecified, PurposeAuthzInstance, PurposeMilestones, PurposeOrganization, PurposeIdPFormCallback}
+
+var _PurposeNameToValueMap = map[string]Purpose{
+	_PurposeName[0:11]:       PurposeUnspecified,
+	_PurposeLowerName[0:11]:  PurposeUnspecified,
+	_PurposeName[11:25]:      PurposeAuthzInstance,
+	_PurposeLowerName[11:25]: PurposeAuthzInstance,
+	_PurposeName[25:35]:      PurposeMilestones,
+	_PurposeLowerName[25:35]: PurposeMilestones,
+	_PurposeName[35:47]:      PurposeOrganization,
+	_PurposeLowerName[35:47]: PurposeOrganization,
+	_PurposeName[47:65]:      PurposeIdPFormCallback,
+	_PurposeLowerName[47:65]: PurposeIdPFormCallback,
+}
+
+var _PurposeNames = []string{
+	_PurposeName[0:11],
+	_PurposeName[11:25],
+	_PurposeName[25:35],
+	_PurposeName[35:47],
+	_PurposeName[47:65],
+}
+
+// PurposeString retrieves an enum value from the enum constants string name.
+// Throws an error if the param is not part of the enum.
+func PurposeString(s string) (Purpose, error) {
+	if val, ok := _PurposeNameToValueMap[s]; ok {
+		return val, nil
+	}
+
+	if val, ok := _PurposeNameToValueMap[strings.ToLower(s)]; ok {
+		return val, nil
+	}
+	return 0, fmt.Errorf("%s does not belong to Purpose values", s)
+}
+
+// PurposeValues returns all values of the enum
+func PurposeValues() []Purpose {
+	return _PurposeValues
+}
+
+// PurposeStrings returns a slice of all String values of the enum
+func PurposeStrings() []string {
+	strs := make([]string, len(_PurposeNames))
+	copy(strs, _PurposeNames)
+	return strs
+}
+
+// IsAPurpose returns "true" if the value is listed in the enum definition. "false" otherwise
+func (i Purpose) IsAPurpose() bool {
+	for _, v := range _PurposeValues {
+		if i == v {
+			return true
+		}
+	}
+	return false
+}

backend/command/receiver/instance.go

@@ -1,6 +1,10 @@
 package receiver
 
-import "context"
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/receiver/cache"
+)
 
 type InstanceState uint8
 
@@ -16,6 +20,31 @@ type Instance struct {
 	Domains []*Domain
 }
 
+type InstanceIndex uint8
+
+var InstanceIndices = []InstanceIndex{
+	InstanceByID,
+	InstanceByDomain,
+}
+
+const (
+	InstanceByID InstanceIndex = iota
+	InstanceByDomain
+)
+
+var _ cache.Entry[InstanceIndex, string] = (*Instance)(nil)
+
+// Keys implements [cache.Entry].
+func (i *Instance) Keys(index InstanceIndex) (key []string) {
+	switch index {
+	case InstanceByID:
+		return []string{i.ID}
+	case InstanceByDomain:
+		return []string{i.Name}
+	}
+	return nil
+}
+
 type InstanceManipulator interface {
 	Create(ctx context.Context, instance *Instance) error
 	Delete(ctx context.Context, instance *Instance) error

backend/command/v2/api/doc.go

@@ -0,0 +1,6 @@
+// The API package implements the protobuf stubs
+
+// It uses the Chain of responsibility pattern to handle requests in a modular way
+// It implements the client or invoker of the command pattern.
+// The client is responsible for creating the concrete command and setting its receiver.
+package api

backend/command/v2/api/user/v2/email.go

@@ -0,0 +1,35 @@
+package userv2
+
+import (
+	"context"
+
+	"github.com/muhlemmer/gu"
+	"github.com/zitadel/zitadel/backend/command/v2/domain"
+	"github.com/zitadel/zitadel/pkg/grpc/user/v2"
+)
+
+func (s *Server) SetEmail(ctx context.Context, req *user.SetEmailRequest) (resp *user.SetEmailResponse, err error) {
+	request := &domain.SetUserEmail{
+		UserID: req.GetUserId(),
+		Email:  req.GetEmail(),
+	}
+	switch req.GetVerification().(type) {
+	case *user.SetEmailRequest_IsVerified:
+		request.IsVerified = gu.Ptr(req.GetIsVerified())
+	case *user.SetEmailRequest_SendCode:
+		request.SendCode = &domain.SendCode{
+			URLTemplate: req.GetSendCode().UrlTemplate,
+		}
+	case *user.SetEmailRequest_ReturnCode:
+		request.ReturnCode = new(domain.ReturnCode)
+	}
+	if err := s.domain.SetUserEmail(ctx, request); err != nil {
+		return nil, err
+	}
+
+	response := new(user.SetEmailResponse)
+	if request.ReturnCode != nil {
+		response.VerificationCode = &request.ReturnCode.Code
+	}
+	return response, nil
+}

backend/command/v2/api/user/v2/server.go

@@ -0,0 +1,12 @@
+package userv2
+
+import (
+	"go.opentelemetry.io/otel/trace"
+
+	"github.com/zitadel/zitadel/backend/command/v2/domain"
+)
+
+type Server struct {
+	tracer trace.Tracer
+	domain *domain.Domain
+}

backend/command/v2/domain/command/generate_code.go

@@ -0,0 +1,41 @@
+package command
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/v2/pattern"
+	"github.com/zitadel/zitadel/internal/crypto"
+)
+
+type generateCode struct {
+	set       func(code string)
+	generator pattern.Query[crypto.Generator]
+}
+
+func GenerateCode(set func(code string), generator pattern.Query[crypto.Generator]) *generateCode {
+	return &generateCode{
+		set:       set,
+		generator: generator,
+	}
+}
+
+var _ pattern.Command = (*generateCode)(nil)
+
+// Execute implements [pattern.Command].
+func (cmd *generateCode) Execute(ctx context.Context) error {
+	if err := cmd.generator.Execute(ctx); err != nil {
+		return err
+	}
+	value, code, err := crypto.NewCode(cmd.generator.Result())
+	_ = value
+	if err != nil {
+		return err
+	}
+	cmd.set(code)
+	return nil
+}
+
+// Name implements [pattern.Command].
+func (*generateCode) Name() string {
+	return "command.generate_code"
+}

backend/command/v2/domain/command/send_email_code.go

@@ -0,0 +1,41 @@
+package command
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/v2/pattern"
+)
+
+var _ pattern.Command = (*sendEmailCode)(nil)
+
+type sendEmailCode struct {
+	UserID      string  `json:"userId"`
+	Email       string  `json:"email"`
+	URLTemplate *string `json:"urlTemplate"`
+	code        string  `json:"-"`
+}
+
+func SendEmailCode(userID, email string, urlTemplate *string) pattern.Command {
+	cmd := &sendEmailCode{
+		UserID:      userID,
+		Email:       email,
+		URLTemplate: urlTemplate,
+	}
+
+	return pattern.Batch(GenerateCode(cmd.SetCode, generateCode))
+}
+
+// Name implements [pattern.Command].
+func (c *sendEmailCode) Name() string {
+	return "user.v2.email.send_code"
+}
+
+// Execute implements [pattern.Command].
+func (c *sendEmailCode) Execute(ctx context.Context) error {
+	// Implementation of the command execution
+	return nil
+}
+
+func (c *sendEmailCode) SetCode(code string) {
+	c.code = code
+}

backend/command/v2/domain/command/set_email.go

@@ -0,0 +1,39 @@
+package command
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/v2/storage/eventstore"
+)
+
+var (
+	_ eventstore.EventCommander = (*setEmail)(nil)
+)
+
+type setEmail struct {
+	UserID string `json:"userId"`
+	Email  string `json:"email"`
+}
+
+func SetEmail(userID, email string) *setEmail {
+	return &setEmail{
+		UserID: userID,
+		Email:  email,
+	}
+}
+
+// Event implements [eventstore.EventCommander].
+func (c *setEmail) Event() *eventstore.Event {
+	panic("unimplemented")
+}
+
+// Name implements [pattern.Command].
+func (c *setEmail) Name() string {
+	return "user.v2.set_email"
+}
+
+// Execute implements [pattern.Command].
+func (c *setEmail) Execute(ctx context.Context) error {
+	// Implementation of the command execution
+	return nil
+}

backend/command/v2/domain/command/verify_email.go

@@ -0,0 +1,32 @@
+package command
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/v2/pattern"
+)
+
+var _ pattern.Command = (*verifyEmail)(nil)
+
+type verifyEmail struct {
+	UserID string `json:"userId"`
+	Email  string `json:"email"`
+}
+
+func VerifyEmail(userID, email string) *verifyEmail {
+	return &verifyEmail{
+		UserID: userID,
+		Email:  email,
+	}
+}
+
+// Name implements [pattern.Command].
+func (c *verifyEmail) Name() string {
+	return "user.v2.verify_email"
+}
+
+// Execute implements [pattern.Command].
+func (c *verifyEmail) Execute(ctx context.Context) error {
+	// Implementation of the command execution
+	return nil
+}

backend/command/v2/domain/domain.go

@@ -0,0 +1,13 @@
+package domain
+
+import (
+	"github.com/zitadel/zitadel/backend/command/v2/storage/database"
+	"github.com/zitadel/zitadel/internal/crypto"
+	"go.opentelemetry.io/otel/trace"
+)
+
+type Domain struct {
+	pool        database.Pool
+	tracer      trace.Tracer
+	userCodeAlg crypto.EncryptionAlgorithm
+}

backend/command/v2/domain/email.go

@@ -0,0 +1,6 @@
+package domain
+
+type Email struct {
+	Address  string
+	Verified bool
+}

backend/command/v2/domain/query/encryption_generator.go

@@ -0,0 +1,42 @@
+package query
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/internal/crypto"
+)
+
+type encryptionConfigReceiver interface {
+	GetEncryptionConfig(ctx context.Context) (*crypto.GeneratorConfig, error)
+}
+
+type encryptionGenerator struct {
+	receiver  encryptionConfigReceiver
+	algorithm crypto.EncryptionAlgorithm
+
+	res crypto.Generator
+}
+
+func QueryEncryptionGenerator(receiver encryptionConfigReceiver, algorithm crypto.EncryptionAlgorithm) *encryptionGenerator {
+	return &encryptionGenerator{
+		receiver:  receiver,
+		algorithm: algorithm,
+	}
+}
+
+func (q *encryptionGenerator) Execute(ctx context.Context) error {
+	config, err := q.receiver.GetEncryptionConfig(ctx)
+	if err != nil {
+		return err
+	}
+	q.res = crypto.NewEncryptionGenerator(*config, q.algorithm)
+	return nil
+}
+
+func (q *encryptionGenerator) Name() string {
+	return "query.encryption_generator"
+}
+
+func (q *encryptionGenerator) Result() crypto.Generator {
+	return q.res
+}

backend/command/v2/domain/query/return_email_code.go

@@ -0,0 +1,38 @@
+package query
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/v2/pattern"
+)
+
+var _ pattern.Query[string] = (*returnEmailCode)(nil)
+
+type returnEmailCode struct {
+	UserID string `json:"userId"`
+	Email  string `json:"email"`
+	code   string `json:"-"`
+}
+
+func ReturnEmailCode(userID, email string) *returnEmailCode {
+	return &returnEmailCode{
+		UserID: userID,
+		Email:  email,
+	}
+}
+
+// Name implements [pattern.Command].
+func (c *returnEmailCode) Name() string {
+	return "user.v2.email.return_code"
+}
+
+// Execute implements [pattern.Command].
+func (c *returnEmailCode) Execute(ctx context.Context) error {
+	// Implementation of the command execution
+	return nil
+}
+
+// Result implements [pattern.Query].
+func (c *returnEmailCode) Result() string {
+	return c.code
+}

backend/command/v2/domain/query/user_by_id.go

@@ -0,0 +1,38 @@
+package query
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/v2/domain"
+	"github.com/zitadel/zitadel/backend/command/v2/pattern"
+	"github.com/zitadel/zitadel/backend/command/v2/storage/database"
+)
+
+type UserByIDQuery struct {
+	querier database.Querier
+	UserID  string `json:"userId"`
+	res     *domain.User
+}
+
+var _ pattern.Query[*domain.User] = (*UserByIDQuery)(nil)
+
+// Name implements [pattern.Command].
+func (q *UserByIDQuery) Name() string {
+	return "user.v2.by_id"
+}
+
+// Execute implements [pattern.Command].
+func (q *UserByIDQuery) Execute(ctx context.Context) error {
+	var res *domain.User
+	err := q.querier.QueryRow(ctx, "SELECT id, username, email FROM users WHERE id = $1", q.UserID).Scan(&res.ID, &res.Username, &res.Email.Address)
+	if err != nil {
+		return err
+	}
+	q.res = res
+	return nil
+}
+
+// Result implements [pattern.Query].
+func (q *UserByIDQuery) Result() *domain.User {
+	return q.res
+}

backend/command/v2/domain/user.go

@@ -0,0 +1,77 @@
+package domain
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/v2/domain/command"
+	"github.com/zitadel/zitadel/backend/command/v2/domain/query"
+	"github.com/zitadel/zitadel/backend/command/v2/pattern"
+	"github.com/zitadel/zitadel/backend/command/v2/storage/database"
+	"github.com/zitadel/zitadel/backend/command/v2/telemetry/tracing"
+)
+
+type User struct {
+	ID       string
+	Username string
+	Email    Email
+}
+
+type SetUserEmail struct {
+	UserID string
+	Email  string
+
+	IsVerified *bool
+	ReturnCode *ReturnCode
+	SendCode   *SendCode
+
+	code   string
+	client database.QueryExecutor
+}
+
+func (e *SetUserEmail) SetCode(code string) {
+	e.code = code
+}
+
+type ReturnCode struct {
+	// Code is the code to be sent to the user
+	Code string
+}
+
+type SendCode struct {
+	// URLTemplate is the template for the URL that is rendered into the message
+	URLTemplate *string
+}
+
+func (d *Domain) SetUserEmail(ctx context.Context, req *SetUserEmail) error {
+	batch := pattern.Batch(
+		tracing.Trace(d.tracer, command.SetEmail(req.UserID, req.Email)),
+	)
+
+	if req.IsVerified == nil {
+		batch.Append(command.GenerateCode(
+			req.SetCode,
+			query.QueryEncryptionGenerator(
+				database.Query(d.pool),
+				d.userCodeAlg,
+			),
+		))
+	} else {
+		batch.Append(command.VerifyEmail(req.UserID, req.Email))
+	}
+
+	// if !req.GetVerification().GetIsVerified() {
+	// 	batch.
+
+	// switch req.GetVerification().(type) {
+	// case *user.SetEmailRequest_IsVerified:
+	// 	batch.Append(tracing.Trace(s.tracer, command.VerifyEmail(req.GetUserId(), req.GetEmail())))
+	// case *user.SetEmailRequest_SendCode:
+	// 	batch.Append(tracing.Trace(s.tracer, command.SendEmailCode(req.GetUserId(), req.GetEmail(), req.GetSendCode().UrlTemplate)))
+	// case *user.SetEmailRequest_ReturnCode:
+	// 	batch.Append(tracing.Trace(s.tracer, query.ReturnEmailCode(req.GetUserId(), req.GetEmail())))
+	// }
+
+	// if err := batch.Execute(ctx); err != nil {
+	// 	return nil, err
+	// }
+}

backend/command/v2/pattern/command.go

@@ -0,0 +1,100 @@
+package pattern
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/command/v2/storage/database"
+)
+
+// Command implements the command pattern.
+// It is used to encapsulate a request as an object, thereby allowing for parameterization of clients with queues, requests, and operations.
+// The command pattern allows for the decoupling of the sender and receiver of a request.
+// It is often used in conjunction with the invoker pattern, which is responsible for executing the command.
+// The command pattern is a behavioral design pattern that turns a request into a stand-alone object.
+// This object contains all the information about the request.
+// The command pattern is useful for implementing undo/redo functionality, logging, and queuing requests.
+// It is also useful for implementing the macro command pattern, which allows for the execution of a series of commands as a single command.
+// The command pattern is also used in event-driven architectures, where events are encapsulated as commands.
+type Command interface {
+	Execute(ctx context.Context) error
+	Name() string
+}
+
+type Query[T any] interface {
+	Command
+	Result() T
+}
+
+type Invoker struct{}
+
+// func bla() {
+// 	sync.Pool{
+// 		New: func() any {
+// 			return new(Invoker)
+// 		},
+// 	}
+// }
+
+type Transaction struct {
+	beginner database.Beginner
+	cmd      Command
+	opts     *database.TransactionOptions
+}
+
+func (t *Transaction) Execute(ctx context.Context) error {
+	tx, err := t.beginner.Begin(ctx, t.opts)
+	if err != nil {
+		return err
+	}
+	defer func() { err = tx.End(ctx, err) }()
+	return t.cmd.Execute(ctx)
+}
+
+func (t *Transaction) Name() string {
+	return t.cmd.Name()
+}
+
+type batch struct {
+	Commands []Command
+}
+
+func Batch(cmds ...Command) *batch {
+	return &batch{
+		Commands: cmds,
+	}
+}
+
+func (b *batch) Execute(ctx context.Context) error {
+	for _, cmd := range b.Commands {
+		if err := cmd.Execute(ctx); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (b *batch) Name() string {
+	return "batch"
+}
+
+func (b *batch) Append(cmds ...Command) {
+	b.Commands = append(b.Commands, cmds...)
+}
+
+type NoopCommand struct{}
+
+func (c *NoopCommand) Execute(_ context.Context) error {
+	return nil
+}
+func (c *NoopCommand) Name() string {
+	return "noop"
+}
+
+type NoopQuery[T any] struct {
+	NoopCommand
+}
+
+func (q *NoopQuery[T]) Result() T {
+	var zero T
+	return zero
+}

backend/command/v2/storage/database/config.go

@@ -0,0 +1,9 @@
+package database
+
+import (
+	"context"
+)
+
+type Connector interface {
+	Connect(ctx context.Context) (Pool, error)
+}

backend/command/v2/storage/database/database.go

@@ -0,0 +1,54 @@
+package database
+
+import (
+	"context"
+)
+
+var (
+	db *database
+)
+
+type database struct {
+	connector Connector
+	pool      Pool
+}
+
+type Pool interface {
+	Beginner
+	QueryExecutor
+
+	Acquire(ctx context.Context) (Client, error)
+	Close(ctx context.Context) error
+}
+
+type Client interface {
+	Beginner
+	QueryExecutor
+
+	Release(ctx context.Context) error
+}
+
+type Querier interface {
+	Query(ctx context.Context, stmt string, args ...any) (Rows, error)
+	QueryRow(ctx context.Context, stmt string, args ...any) Row
+}
+
+type Executor interface {
+	Exec(ctx context.Context, stmt string, args ...any) error
+}
+
+type Row interface {
+	Scan(dest ...any) error
+}
+
+type Rows interface {
+	Row
+	Next() bool
+	Close() error
+	Err() error
+}
+
+type QueryExecutor interface {
+	Querier
+	Executor
+}

backend/command/v2/storage/database/dialect/config.go

@@ -0,0 +1,92 @@
+package dialect
+
+import (
+	"context"
+	"errors"
+	"reflect"
+
+	"github.com/mitchellh/mapstructure"
+	"github.com/spf13/viper"
+
+	"github.com/zitadel/zitadel/backend/storage/database"
+	"github.com/zitadel/zitadel/backend/storage/database/dialect/postgres"
+)
+
+type Hook struct {
+	Match       func(string) bool
+	Decode      func(config any) (database.Connector, error)
+	Name        string
+	Constructor func() database.Connector
+}
+
+var hooks = []Hook{
+	{
+		Match:       postgres.NameMatcher,
+		Decode:      postgres.DecodeConfig,
+		Name:        postgres.Name,
+		Constructor: func() database.Connector { return new(postgres.Config) },
+	},
+	// {
+	// 	Match:       gosql.NameMatcher,
+	// 	Decode:      gosql.DecodeConfig,
+	// 	Name:        gosql.Name,
+	// 	Constructor: func() database.Connector { return new(gosql.Config) },
+	// },
+}
+
+type Config struct {
+	Dialects map[string]any `mapstructure:",remain" yaml:",inline"`
+
+	connector database.Connector
+}
+
+func (c Config) Connect(ctx context.Context) (database.Pool, error) {
+	if len(c.Dialects) != 1 {
+		return nil, errors.New("Exactly one dialect must be configured")
+	}
+
+	return c.connector.Connect(ctx)
+}
+
+// Hooks implements [configure.Unmarshaller].
+func (c Config) Hooks() []viper.DecoderConfigOption {
+	return []viper.DecoderConfigOption{
+		viper.DecodeHook(decodeHook),
+	}
+}
+
+func decodeHook(from, to reflect.Value) (_ any, err error) {
+	if to.Type() != reflect.TypeOf(Config{}) {
+		return from.Interface(), nil
+	}
+
+	config := new(Config)
+	if err = mapstructure.Decode(from.Interface(), config); err != nil {
+		return nil, err
+	}
+
+	if err = config.decodeDialect(); err != nil {
+		return nil, err
+	}
+
+	return config, nil
+}
+
+func (c *Config) decodeDialect() error {
+	for _, hook := range hooks {
+		for name, config := range c.Dialects {
+			if !hook.Match(name) {
+				continue
+			}
+
+			connector, err := hook.Decode(config)
+			if err != nil {
+				return err
+			}
+
+			c.connector = connector
+			return nil
+		}
+	}
+	return errors.New("no dialect found")
+}

backend/command/v2/storage/database/dialect/postgres/config.go

@@ -0,0 +1,80 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"slices"
+	"strings"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+	"github.com/mitchellh/mapstructure"
+
+	"github.com/zitadel/zitadel/backend/command/v2/storage/database"
+)
+
+var (
+	_    database.Connector = (*Config)(nil)
+	Name                    = "postgres"
+)
+
+type Config struct {
+	config *pgxpool.Config
+
+	// Host               string
+	// Port               int32
+	// Database           string
+	// MaxOpenConns       uint32
+	// MaxIdleConns       uint32
+	// MaxConnLifetime    time.Duration
+	// MaxConnIdleTime    time.Duration
+	// User               User
+	// // Additional options to be appended as options=<Options>
+	// // The value will be taken as is. Multiple options are space separated.
+	// Options string
+
+	configuredFields []string
+}
+
+// Connect implements [database.Connector].
+func (c *Config) Connect(ctx context.Context) (database.Pool, error) {
+	pool, err := pgxpool.NewWithConfig(ctx, c.config)
+	if err != nil {
+		return nil, err
+	}
+	if err = pool.Ping(ctx); err != nil {
+		return nil, err
+	}
+	return &pgxPool{pool}, nil
+}
+
+func NameMatcher(name string) bool {
+	return slices.Contains([]string{"postgres", "pg"}, strings.ToLower(name))
+}
+
+func DecodeConfig(input any) (database.Connector, error) {
+	switch c := input.(type) {
+	case string:
+		config, err := pgxpool.ParseConfig(c)
+		if err != nil {
+			return nil, err
+		}
+		return &Config{config: config}, nil
+	case map[string]any:
+		connector := new(Config)
+		decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
+			DecodeHook:       mapstructure.StringToTimeDurationHookFunc(),
+			WeaklyTypedInput: true,
+			Result:           connector,
+		})
+		if err != nil {
+			return nil, err
+		}
+		if err = decoder.Decode(c); err != nil {
+			return nil, err
+		}
+		return &Config{
+			config: &pgxpool.Config{},
+		}, nil
+	}
+	return nil, errors.New("invalid configuration")
+}

backend/command/v2/storage/database/dialect/postgres/conn.go

@@ -0,0 +1,48 @@
+package postgres
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"github.com/zitadel/zitadel/backend/command/v2/storage/database"
+)
+
+type pgxConn struct{ *pgxpool.Conn }
+
+var _ database.Client = (*pgxConn)(nil)
+
+// Release implements [database.Client].
+func (c *pgxConn) Release(_ context.Context) error {
+	c.Conn.Release()
+	return nil
+}
+
+// Begin implements [database.Client].
+func (c *pgxConn) Begin(ctx context.Context, opts *database.TransactionOptions) (database.Transaction, error) {
+	tx, err := c.Conn.BeginTx(ctx, transactionOptionsToPgx(opts))
+	if err != nil {
+		return nil, err
+	}
+	return &pgxTx{tx}, nil
+}
+
+// Query implements sql.Client.
+// Subtle: this method shadows the method (*Conn).Query of pgxConn.Conn.
+func (c *pgxConn) Query(ctx context.Context, sql string, args ...any) (database.Rows, error) {
+	rows, err := c.Conn.Query(ctx, sql, args...)
+	return &Rows{rows}, err
+}
+
+// QueryRow implements sql.Client.
+// Subtle: this method shadows the method (*Conn).QueryRow of pgxConn.Conn.
+func (c *pgxConn) QueryRow(ctx context.Context, sql string, args ...any) database.Row {
+	return c.Conn.QueryRow(ctx, sql, args...)
+}
+
+// Exec implements [database.Pool].
+// Subtle: this method shadows the method (Pool).Exec of pgxPool.Pool.
+func (c *pgxConn) Exec(ctx context.Context, sql string, args ...any) error {
+	_, err := c.Conn.Exec(ctx, sql, args...)
+	return err
+}

backend/command/v2/storage/database/dialect/postgres/pool.go

@@ -0,0 +1,57 @@
+package postgres
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"github.com/zitadel/zitadel/backend/command/v2/storage/database"
+)
+
+type pgxPool struct{ *pgxpool.Pool }
+
+var _ database.Pool = (*pgxPool)(nil)
+
+// Acquire implements [database.Pool].
+func (c *pgxPool) Acquire(ctx context.Context) (database.Client, error) {
+	conn, err := c.Pool.Acquire(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return &pgxConn{conn}, nil
+}
+
+// Query implements [database.Pool].
+// Subtle: this method shadows the method (Pool).Query of pgxPool.Pool.
+func (c *pgxPool) Query(ctx context.Context, sql string, args ...any) (database.Rows, error) {
+	rows, err := c.Pool.Query(ctx, sql, args...)
+	return &Rows{rows}, err
+}
+
+// QueryRow implements [database.Pool].
+// Subtle: this method shadows the method (Pool).QueryRow of pgxPool.Pool.
+func (c *pgxPool) QueryRow(ctx context.Context, sql string, args ...any) database.Row {
+	return c.Pool.QueryRow(ctx, sql, args...)
+}
+
+// Exec implements [database.Pool].
+// Subtle: this method shadows the method (Pool).Exec of pgxPool.Pool.
+func (c *pgxPool) Exec(ctx context.Context, sql string, args ...any) error {
+	_, err := c.Pool.Exec(ctx, sql, args...)
+	return err
+}
+
+// Begin implements [database.Pool].
+func (c *pgxPool) Begin(ctx context.Context, opts *database.TransactionOptions) (database.Transaction, error) {
+	tx, err := c.Pool.BeginTx(ctx, transactionOptionsToPgx(opts))
+	if err != nil {
+		return nil, err
+	}
+	return &pgxTx{tx}, nil
+}
+
+// Close implements [database.Pool].
+func (c *pgxPool) Close(_ context.Context) error {
+	c.Pool.Close()
+	return nil
+}

backend/command/v2/storage/database/dialect/postgres/rows.go

@@ -0,0 +1,18 @@
+package postgres
+
+import (
+	"github.com/jackc/pgx/v5"
+
+	"github.com/zitadel/zitadel/backend/command/v2/storage/database"
+)
+
+var _ database.Rows = (*Rows)(nil)
+
+type Rows struct{ pgx.Rows }
+
+// Close implements [database.Rows].
+// Subtle: this method shadows the method (Rows).Close of Rows.Rows.
+func (r *Rows) Close() error {
+	r.Rows.Close()
+	return nil
+}

backend/command/v2/storage/database/dialect/postgres/tx.go

@@ -0,0 +1,95 @@
+package postgres
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5"
+
+	"github.com/zitadel/zitadel/backend/command/v2/storage/database"
+)
+
+type pgxTx struct{ pgx.Tx }
+
+var _ database.Transaction = (*pgxTx)(nil)
+
+// Commit implements [database.Transaction].
+func (tx *pgxTx) Commit(ctx context.Context) error {
+	return tx.Tx.Commit(ctx)
+}
+
+// Rollback implements [database.Transaction].
+func (tx *pgxTx) Rollback(ctx context.Context) error {
+	return tx.Tx.Rollback(ctx)
+}
+
+// End implements [database.Transaction].
+func (tx *pgxTx) End(ctx context.Context, err error) error {
+	if err != nil {
+		tx.Rollback(ctx)
+		return err
+	}
+	return tx.Commit(ctx)
+}
+
+// Query implements [database.Transaction].
+// Subtle: this method shadows the method (Tx).Query of pgxTx.Tx.
+func (tx *pgxTx) Query(ctx context.Context, sql string, args ...any) (database.Rows, error) {
+	rows, err := tx.Tx.Query(ctx, sql, args...)
+	return &Rows{rows}, err
+}
+
+// QueryRow implements [database.Transaction].
+// Subtle: this method shadows the method (Tx).QueryRow of pgxTx.Tx.
+func (tx *pgxTx) QueryRow(ctx context.Context, sql string, args ...any) database.Row {
+	return tx.Tx.QueryRow(ctx, sql, args...)
+}
+
+// Exec implements [database.Transaction].
+// Subtle: this method shadows the method (Pool).Exec of pgxPool.Pool.
+func (tx *pgxTx) Exec(ctx context.Context, sql string, args ...any) error {
+	_, err := tx.Tx.Exec(ctx, sql, args...)
+	return err
+}
+
+// Begin implements [database.Transaction].
+// As postgres does not support nested transactions we use savepoints to emulate them.
+func (tx *pgxTx) Begin(ctx context.Context) (database.Transaction, error) {
+	savepoint, err := tx.Tx.Begin(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return &pgxTx{savepoint}, nil
+}
+
+func transactionOptionsToPgx(opts *database.TransactionOptions) pgx.TxOptions {
+	if opts == nil {
+		return pgx.TxOptions{}
+	}
+
+	return pgx.TxOptions{
+		IsoLevel:   isolationToPgx(opts.IsolationLevel),
+		AccessMode: accessModeToPgx(opts.AccessMode),
+	}
+}
+
+func isolationToPgx(isolation database.IsolationLevel) pgx.TxIsoLevel {
+	switch isolation {
+	case database.IsolationLevelSerializable:
+		return pgx.Serializable
+	case database.IsolationLevelReadCommitted:
+		return pgx.ReadCommitted
+	default:
+		return pgx.Serializable
+	}
+}
+
+func accessModeToPgx(accessMode database.AccessMode) pgx.TxAccessMode {
+	switch accessMode {
+	case database.AccessModeReadWrite:
+		return pgx.ReadWrite
+	case database.AccessModeReadOnly:
+		return pgx.ReadOnly
+	default:
+		return pgx.ReadWrite
+	}
+}

backend/command/v2/storage/database/secret_generator.go

@@ -0,0 +1,39 @@
+package database
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/internal/crypto"
+)
+
+type query struct{ Querier }
+
+func Query(querier Querier) *query {
+	return &query{Querier: querier}
+}
+
+const getEncryptionConfigQuery = "SELECT" +
+	" length" +
+	", expiry" +
+	", should_include_lower_letters" +
+	", should_include_upper_letters" +
+	", should_include_digits" +
+	", should_include_symbols" +
+	" FROM encryption_config"
+
+func (q query) GetEncryptionConfig(ctx context.Context) (*crypto.GeneratorConfig, error) {
+	var config crypto.GeneratorConfig
+	row := q.QueryRow(ctx, getEncryptionConfigQuery)
+	err := row.Scan(
+		&config.Length,
+		&config.Expiry,
+		&config.IncludeLowerLetters,
+		&config.IncludeUpperLetters,
+		&config.IncludeDigits,
+		&config.IncludeSymbols,
+	)
+	if err != nil {
+		return nil, err
+	}
+	return &config, nil
+}

backend/command/v2/storage/database/tx.go

@@ -0,0 +1,36 @@
+package database
+
+import "context"
+
+type Transaction interface {
+	Commit(ctx context.Context) error
+	Rollback(ctx context.Context) error
+	End(ctx context.Context, err error) error
+
+	Begin(ctx context.Context) (Transaction, error)
+
+	QueryExecutor
+}
+
+type Beginner interface {
+	Begin(ctx context.Context, opts *TransactionOptions) (Transaction, error)
+}
+
+type TransactionOptions struct {
+	IsolationLevel IsolationLevel
+	AccessMode     AccessMode
+}
+
+type IsolationLevel uint8
+
+const (
+	IsolationLevelSerializable IsolationLevel = iota
+	IsolationLevelReadCommitted
+)
+
+type AccessMode uint8
+
+const (
+	AccessModeReadWrite AccessMode = iota
+	AccessModeReadOnly
+)

backend/command/v2/storage/eventstore/event.go

@@ -0,0 +1,13 @@
+package eventstore
+
+import "github.com/zitadel/zitadel/backend/command/v2/pattern"
+
+type Event struct {
+	AggregateType string `json:"aggregateType"`
+	AggregateID   string `json:"aggregateId"`
+}
+
+type EventCommander interface {
+	pattern.Command
+	Event() *Event
+}

backend/command/v2/telemetry/tracing/command.go

@@ -0,0 +1,55 @@
+package tracing
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel/trace"
+
+	"github.com/zitadel/zitadel/backend/command/v2/pattern"
+)
+
+type command struct {
+	trace.Tracer
+	cmd pattern.Command
+}
+
+func Trace(tracer trace.Tracer, cmd pattern.Command) pattern.Command {
+	return &command{
+		Tracer: tracer,
+		cmd:    cmd,
+	}
+}
+
+func (cmd *command) Name() string {
+	return cmd.cmd.Name()
+}
+
+func (cmd *command) Execute(ctx context.Context) error {
+	ctx, span := cmd.Tracer.Start(ctx, cmd.Name())
+	defer span.End()
+
+	err := cmd.cmd.Execute(ctx)
+	if err != nil {
+		span.RecordError(err)
+	}
+	return err
+}
+
+type query[T any] struct {
+	command
+	query pattern.Query[T]
+}
+
+func Query[T any](tracer trace.Tracer, q pattern.Query[T]) pattern.Query[T] {
+	return &query[T]{
+		command: command{
+			Tracer: tracer,
+			cmd:    q,
+		},
+		query: q,
+	}
+}
+
+func (q *query[T]) Result() T {
+	return q.query.Result()
+}

backend/v3/api/instance/v2/server.go

@@ -0,0 +1,19 @@
+package v2
+
+import (
+	"github.com/zitadel/zitadel/backend/v3/telemetry/logging"
+	"github.com/zitadel/zitadel/backend/v3/telemetry/tracing"
+)
+
+var (
+	logger logging.Logger
+	tracer tracing.Tracer
+)
+
+func SetLogger(l logging.Logger) {
+	logger = l
+}
+
+func SetTracer(t tracing.Tracer) {
+	tracer = t
+}

backend/v3/api/user/v2/email.go

@@ -0,0 +1,93 @@
+package userv2
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/v3/domain"
+	"github.com/zitadel/zitadel/pkg/grpc/user/v2"
+)
+
+func SetEmail(ctx context.Context, req *user.SetEmailRequest) (resp *user.SetEmailResponse, err error) {
+	var (
+		verification domain.SetEmailOpt
+		returnCode   *domain.ReturnCodeCommand
+	)
+
+	switch req.GetVerification().(type) {
+	case *user.SetEmailRequest_IsVerified:
+		verification = domain.NewEmailVerifiedCommand(req.GetUserId(), req.GetIsVerified())
+	case *user.SetEmailRequest_SendCode:
+		verification = domain.NewSendCodeCommand(req.GetUserId(), req.GetSendCode().UrlTemplate)
+	case *user.SetEmailRequest_ReturnCode:
+		returnCode = domain.NewReturnCodeCommand(req.GetUserId())
+		verification = returnCode
+	default:
+		verification = domain.NewSendCodeCommand(req.GetUserId(), nil)
+	}
+
+	err = domain.Invoke(ctx, domain.NewSetEmailCommand(req.GetUserId(), req.GetEmail(), verification))
+	if err != nil {
+		return nil, err
+	}
+
+	var code *string
+	if returnCode != nil && returnCode.Code != "" {
+		code = &returnCode.Code
+	}
+
+	return &user.SetEmailResponse{
+		VerificationCode: code,
+	}, nil
+}
+
+func SendEmailCode(ctx context.Context, req *user.SendEmailCodeRequest) (resp *user.SendEmailCodeResponse, err error) {
+	var (
+		returnCode *domain.ReturnCodeCommand
+		cmd        domain.Commander
+	)
+
+	switch req.GetVerification().(type) {
+	case *user.SendEmailCodeRequest_SendCode:
+		cmd = domain.NewSendCodeCommand(req.GetUserId(), req.GetSendCode().UrlTemplate)
+	case *user.SendEmailCodeRequest_ReturnCode:
+		returnCode = domain.NewReturnCodeCommand(req.GetUserId())
+		cmd = returnCode
+	default:
+		cmd = domain.NewSendCodeCommand(req.GetUserId(), req.GetSendCode().UrlTemplate)
+	}
+	err = domain.Invoke(ctx, cmd)
+	if err != nil {
+		return nil, err
+	}
+	resp = new(user.SendEmailCodeResponse)
+	if returnCode != nil {
+		resp.VerificationCode = &returnCode.Code
+	}
+	return resp, nil
+}
+
+func ResendEmailCode(ctx context.Context, req *user.ResendEmailCodeRequest) (resp *user.SendEmailCodeResponse, err error) {
+	var (
+		returnCode *domain.ReturnCodeCommand
+		cmd        domain.Commander
+	)
+
+	switch req.GetVerification().(type) {
+	case *user.ResendEmailCodeRequest_SendCode:
+		cmd = domain.NewSendCodeCommand(req.GetUserId(), req.GetSendCode().UrlTemplate)
+	case *user.ResendEmailCodeRequest_ReturnCode:
+		returnCode = domain.NewReturnCodeCommand(req.GetUserId())
+		cmd = returnCode
+	default:
+		cmd = domain.NewSendCodeCommand(req.GetUserId(), req.GetSendCode().UrlTemplate)
+	}
+	err = domain.Invoke(ctx, cmd)
+	if err != nil {
+		return nil, err
+	}
+	resp = new(user.SendEmailCodeResponse)
+	if returnCode != nil {
+		resp.VerificationCode = &returnCode.Code
+	}
+	return resp, nil
+}

backend/v3/api/user/v2/server.go

@@ -0,0 +1,19 @@
+package userv2
+
+import (
+	"github.com/zitadel/zitadel/backend/v3/telemetry/logging"
+	"github.com/zitadel/zitadel/backend/v3/telemetry/tracing"
+)
+
+var (
+	logger logging.Logger
+	tracer tracing.Tracer
+)
+
+func SetLogger(l logging.Logger) {
+	logger = l
+}
+
+func SetTracer(t tracing.Tracer) {
+	tracer = t
+}

backend/v3/doc.go

@@ -0,0 +1,12 @@
+// the test used the manly relies on the following patterns:
+// - domain:
+//   - hexagonal architecture, it defines its dependencies as interfaces and the dependencies must use the objects defined by this package
+//   - command pattern which implements the changes
+//   - the invoker decorates the commands by checking for events and tracing
+//   - the database connections are manged in this package
+//   - the database connections are passed to the repositories
+//
+// - storage:
+//   - repository pattern, the repositories are defined as interfaces and the implementations are in the storage package
+//   - the repositories are used by the domain package to access the database
+package v3

backend/v3/domain/command.go

@@ -0,0 +1,105 @@
+package domain
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+type Commander interface {
+	Execute(ctx context.Context, opts *CommandOpts) (err error)
+}
+
+type Invoker interface {
+	Invoke(ctx context.Context, command Commander, opts *CommandOpts) error
+}
+
+type CommandOpts struct {
+	DB      database.QueryExecutor
+	Invoker Invoker
+}
+
+type ensureTxOpts struct {
+	*database.TransactionOptions
+}
+
+type EnsureTransactionOpt func(*ensureTxOpts)
+
+// EnsureTx ensures that the DB is a transaction. If it is not, it will start a new transaction.
+// The returned close function will end the transaction. If the DB is already a transaction, the close function
+// will do nothing because another [Commander] is already responsible for ending the transaction.
+func (o *CommandOpts) EnsureTx(ctx context.Context, opts ...EnsureTransactionOpt) (close func(context.Context, error) error, err error) {
+	beginner, ok := o.DB.(database.Beginner)
+	if !ok {
+		// db is already a transaction
+		return func(_ context.Context, err error) error {
+			return err
+		}, nil
+	}
+
+	txOpts := &ensureTxOpts{
+		TransactionOptions: new(database.TransactionOptions),
+	}
+	for _, opt := range opts {
+		opt(txOpts)
+	}
+
+	tx, err := beginner.Begin(ctx, txOpts.TransactionOptions)
+	if err != nil {
+		return nil, err
+	}
+	o.DB = tx
+
+	return func(ctx context.Context, err error) error {
+		return tx.End(ctx, err)
+	}, nil
+}
+
+// EnsureClient ensures that the o.DB is a client. If it is not, it will get a new client from the [database.Pool].
+// The returned close function will release the client. If the o.DB is already a client or transaction, the close function
+// will do nothing because another [Commander] is already responsible for releasing the client.
+func (o *CommandOpts) EnsureClient(ctx context.Context) (close func(_ context.Context) error, err error) {
+	pool, ok := o.DB.(database.Pool)
+	if !ok {
+		// o.DB is already a client
+		return func(_ context.Context) error {
+			return nil
+		}, nil
+	}
+	client, err := pool.Acquire(ctx)
+	if err != nil {
+		return nil, err
+	}
+	o.DB = client
+	return func(ctx context.Context) error {
+		return client.Release(ctx)
+	}, nil
+}
+
+func (o *CommandOpts) Invoke(ctx context.Context, command Commander) error {
+	if o.Invoker == nil {
+		return command.Execute(ctx, o)
+	}
+	return o.Invoker.Invoke(ctx, command, o)
+}
+
+func DefaultOpts(invoker Invoker) *CommandOpts {
+	if invoker == nil {
+		invoker = &noopInvoker{}
+	}
+	return &CommandOpts{
+		DB:      pool,
+		Invoker: invoker,
+	}
+}
+
+type noopInvoker struct {
+	next Invoker
+}
+
+func (i *noopInvoker) Invoke(ctx context.Context, command Commander, opts *CommandOpts) error {
+	if i.next != nil {
+		return i.next.Invoke(ctx, command, opts)
+	}
+	return command.Execute(ctx, opts)
+}

backend/v3/domain/create_user.go

@@ -0,0 +1,76 @@
+package domain
+
+import (
+	"context"
+
+	v4 "github.com/zitadel/zitadel/backend/v3/storage/database/repository/stmt/v4"
+	"github.com/zitadel/zitadel/backend/v3/storage/eventstore"
+)
+
+type CreateUserCommand struct {
+	user  *User
+	email *SetEmailCommand
+}
+
+var (
+	_ Commander = (*CreateUserCommand)(nil)
+	_ eventer   = (*CreateUserCommand)(nil)
+)
+
+func NewCreateHumanCommand(username string, opts ...CreateHumanOpt) *CreateUserCommand {
+	cmd := &CreateUserCommand{
+		user: &User{
+			User: v4.User{
+				Username: username,
+				Traits:   &v4.Human{},
+			},
+		},
+	}
+
+	for _, opt := range opts {
+		opt.applyOnCreateHuman(cmd)
+	}
+	return cmd
+}
+
+// Events implements [eventer].
+func (c *CreateUserCommand) Events() []*eventstore.Event {
+	panic("unimplemented")
+}
+
+// Execute implements [Commander].
+func (c *CreateUserCommand) Execute(ctx context.Context, opts *CommandOpts) error {
+	if err := c.ensureUserID(); err != nil {
+		return err
+	}
+	c.email.UserID = c.user.ID
+	if err := opts.Invoke(ctx, c.email); err != nil {
+		return err
+	}
+	return nil
+}
+
+type CreateHumanOpt interface {
+	applyOnCreateHuman(*CreateUserCommand)
+}
+
+type createHumanIDOpt string
+
+// applyOnCreateHuman implements [CreateHumanOpt].
+func (c createHumanIDOpt) applyOnCreateHuman(cmd *CreateUserCommand) {
+	cmd.user.ID = string(c)
+}
+
+var _ CreateHumanOpt = (*createHumanIDOpt)(nil)
+
+func CreateHumanWithID(id string) CreateHumanOpt {
+	return createHumanIDOpt(id)
+}
+
+func (c *CreateUserCommand) ensureUserID() (err error) {
+	if c.user.ID != "" {
+		return nil
+	}
+	c.user.ID, err = generateID()
+	return err
+}

backend/v3/domain/crypto.go

@@ -0,0 +1,26 @@
+package domain
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/internal/crypto"
+)
+
+type generateCodeCommand struct {
+	code  string
+	value *crypto.CryptoValue
+}
+
+type CryptoRepository interface {
+	GetEncryptionConfig(ctx context.Context) (*crypto.GeneratorConfig, error)
+}
+
+func (cmd *generateCodeCommand) Execute(ctx context.Context, opts *CommandOpts) error {
+	config, err := cryptoRepo(opts.DB).GetEncryptionConfig(ctx)
+	if err != nil {
+		return err
+	}
+	generator := crypto.NewEncryptionGenerator(*config, userCodeAlgorithm)
+	cmd.value, cmd.code, err = crypto.NewCode(generator)
+	return err
+}

backend/v3/domain/domain.go

@@ -0,0 +1,52 @@
+package domain
+
+import (
+	"math/rand/v2"
+	"strconv"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/cache"
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+	"github.com/zitadel/zitadel/backend/v3/telemetry/tracing"
+	"github.com/zitadel/zitadel/internal/crypto"
+)
+
+var (
+	pool              database.Pool
+	userCodeAlgorithm crypto.EncryptionAlgorithm
+	tracer            tracing.Tracer
+
+	// userRepo     func(database.QueryExecutor) UserRepository
+	instanceRepo func(database.QueryExecutor) InstanceRepository
+	cryptoRepo   func(database.QueryExecutor) CryptoRepository
+	orgRepo      func(database.QueryExecutor) OrgRepository
+
+	instanceCache cache.Cache[string, string, *Instance]
+
+	generateID func() (string, error) = func() (string, error) {
+		return strconv.FormatUint(rand.Uint64(), 10), nil
+	}
+)
+
+func SetPool(p database.Pool) {
+	pool = p
+}
+
+func SetUserCodeAlgorithm(algorithm crypto.EncryptionAlgorithm) {
+	userCodeAlgorithm = algorithm
+}
+
+func SetTracer(t tracing.Tracer) {
+	tracer = t
+}
+
+// func SetUserRepository(repo func(database.QueryExecutor) UserRepository) {
+// 	userRepo = repo
+// }
+
+func SetInstanceRepository(repo func(database.QueryExecutor) InstanceRepository) {
+	instanceRepo = repo
+}
+
+func SetCryptoRepository(repo func(database.QueryExecutor) CryptoRepository) {
+	cryptoRepo = repo
+}

backend/v3/domain/domain_test.go

@@ -0,0 +1,45 @@
+package domain_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+
+	. "github.com/zitadel/zitadel/backend/v3/domain"
+	"github.com/zitadel/zitadel/backend/v3/storage/database/repository"
+	"github.com/zitadel/zitadel/backend/v3/telemetry/tracing"
+)
+
+func TestExample(t *testing.T) {
+	ctx := context.Background()
+
+	// SetPool(pool)
+
+	exporter, err := stdouttrace.New(stdouttrace.WithPrettyPrint())
+	require.NoError(t, err)
+	tracerProvider := sdktrace.NewTracerProvider(
+		sdktrace.WithSyncer(exporter),
+	)
+	otel.SetTracerProvider(tracerProvider)
+	SetTracer(tracing.Tracer{Tracer: tracerProvider.Tracer("test")})
+	defer func() { assert.NoError(t, tracerProvider.Shutdown(ctx)) }()
+
+	SetUserRepository(repository.User)
+	SetInstanceRepository(repository.Instance)
+	SetCryptoRepository(repository.Crypto)
+
+	t.Run("verified email", func(t *testing.T) {
+		err := Invoke(ctx, NewSetEmailCommand("u1", "test@example.com", NewEmailVerifiedCommand("u1", true)))
+		assert.NoError(t, err)
+	})
+
+	t.Run("unverified email", func(t *testing.T) {
+		err := Invoke(ctx, NewSetEmailCommand("u2", "test2@example.com", NewEmailVerifiedCommand("u2", false)))
+		assert.NoError(t, err)
+	})
+}

backend/v3/domain/email_verification.go

@@ -0,0 +1,155 @@
+package domain
+
+import (
+	"context"
+
+	v4 "github.com/zitadel/zitadel/backend/v3/storage/database/repository/stmt/v4"
+)
+
+type EmailVerifiedCommand struct {
+	UserID string `json:"userId"`
+	Email  *Email `json:"email"`
+}
+
+func NewEmailVerifiedCommand(userID string, isVerified bool) *EmailVerifiedCommand {
+	return &EmailVerifiedCommand{
+		UserID: userID,
+		Email: &Email{
+			IsVerified: isVerified,
+		},
+	}
+}
+
+var (
+	_ Commander   = (*EmailVerifiedCommand)(nil)
+	_ SetEmailOpt = (*EmailVerifiedCommand)(nil)
+)
+
+// Execute implements [Commander]
+func (cmd *EmailVerifiedCommand) Execute(ctx context.Context, opts *CommandOpts) error {
+	return userRepo(opts.DB).Human().ByID(cmd.UserID).Exec().SetEmailVerified(ctx, cmd.Email.Address)
+}
+
+// applyOnSetEmail implements [SetEmailOpt]
+func (cmd *EmailVerifiedCommand) applyOnSetEmail(setEmailCmd *SetEmailCommand) {
+	cmd.UserID = setEmailCmd.UserID
+	cmd.Email.Address = setEmailCmd.Email
+	setEmailCmd.verification = cmd
+}
+
+type SendCodeCommand struct {
+	UserID      string  `json:"userId"`
+	Email       string  `json:"email"`
+	URLTemplate *string `json:"urlTemplate"`
+	generator   *generateCodeCommand
+}
+
+var (
+	_ Commander   = (*SendCodeCommand)(nil)
+	_ SetEmailOpt = (*SendCodeCommand)(nil)
+)
+
+func NewSendCodeCommand(userID string, urlTemplate *string) *SendCodeCommand {
+	return &SendCodeCommand{
+		UserID:      userID,
+		generator:   &generateCodeCommand{},
+		URLTemplate: urlTemplate,
+	}
+}
+
+// Execute implements [Commander]
+func (cmd *SendCodeCommand) Execute(ctx context.Context, opts *CommandOpts) error {
+	if err := cmd.ensureEmail(ctx, opts); err != nil {
+		return err
+	}
+	if err := cmd.ensureURL(ctx, opts); err != nil {
+		return err
+	}
+
+	if err := opts.Invoker.Invoke(ctx, cmd.generator, opts); err != nil {
+		return err
+	}
+	// TODO: queue notification
+
+	return nil
+}
+
+func (cmd *SendCodeCommand) ensureEmail(ctx context.Context, opts *CommandOpts) error {
+	if cmd.Email != "" {
+		return nil
+	}
+	email, err := userRepo(opts.DB).Human().ByID(cmd.UserID).Exec().GetEmail(ctx)
+	if err != nil || email.IsVerified {
+		return err
+	}
+	cmd.Email = email.Address
+	return nil
+}
+
+func (cmd *SendCodeCommand) ensureURL(ctx context.Context, opts *CommandOpts) error {
+	if cmd.URLTemplate != nil && *cmd.URLTemplate != "" {
+		return nil
+	}
+	_, _ = ctx, opts
+	// TODO: load default template
+	return nil
+}
+
+// applyOnSetEmail implements [SetEmailOpt]
+func (cmd *SendCodeCommand) applyOnSetEmail(setEmailCmd *SetEmailCommand) {
+	cmd.UserID = setEmailCmd.UserID
+	cmd.Email = setEmailCmd.Email
+	setEmailCmd.verification = cmd
+}
+
+type ReturnCodeCommand struct {
+	UserID    string `json:"userId"`
+	Email     string `json:"email"`
+	Code      string `json:"code"`
+	generator *generateCodeCommand
+}
+
+var (
+	_ Commander   = (*ReturnCodeCommand)(nil)
+	_ SetEmailOpt = (*ReturnCodeCommand)(nil)
+)
+
+func NewReturnCodeCommand(userID string) *ReturnCodeCommand {
+	return &ReturnCodeCommand{
+		UserID:    userID,
+		generator: &generateCodeCommand{},
+	}
+}
+
+// Execute implements [Commander]
+func (cmd *ReturnCodeCommand) Execute(ctx context.Context, opts *CommandOpts) error {
+	if err := cmd.ensureEmail(ctx, opts); err != nil {
+		return err
+	}
+	if err := opts.Invoker.Invoke(ctx, cmd.generator, opts); err != nil {
+		return err
+	}
+	cmd.Code = cmd.generator.code
+	return nil
+}
+
+func (cmd *ReturnCodeCommand) ensureEmail(ctx context.Context, opts *CommandOpts) error {
+	if cmd.Email != "" {
+		return nil
+	}
+	user := v4.UserRepository(opts.DB)
+	user.WithCondition(user.IDCondition(cmd.UserID))
+	email, err := user.he.GetEmail(ctx)
+	if err != nil || email.IsVerified {
+		return err
+	}
+	cmd.Email = email.Address
+	return nil
+}
+
+// applyOnSetEmail implements [SetEmailOpt]
+func (cmd *ReturnCodeCommand) applyOnSetEmail(setEmailCmd *SetEmailCommand) {
+	cmd.UserID = setEmailCmd.UserID
+	cmd.Email = setEmailCmd.Email
+	setEmailCmd.verification = cmd
+}

backend/v3/domain/errors.go

@@ -0,0 +1,7 @@
+package domain
+
+import "errors"
+
+var (
+	ErrNoAdminSpecified = errors.New("at least one admin must be specified")
+)

backend/v3/domain/instance.go

@@ -0,0 +1,36 @@
+package domain
+
+import (
+	"context"
+	"time"
+)
+
+type Instance struct {
+	ID        string    `json:"id"`
+	Name      string    `json:"name"`
+	CreatedAt time.Time `json:"-"`
+	UpdatedAt time.Time `json:"-"`
+	DeletedAt time.Time `json:"-"`
+}
+
+// Keys implements the [cache.Entry].
+func (i *Instance) Keys(index string) (key []string) {
+	// TODO: Return the correct keys for the instance cache, e.g., i.ID, i.Domain
+	return []string{}
+}
+
+type InstanceRepository interface {
+	ByID(ctx context.Context, id string) (*Instance, error)
+	Create(ctx context.Context, instance *Instance) error
+	On(id string) InstanceOperation
+}
+
+type InstanceOperation interface {
+	AdminRepository
+	Update(ctx context.Context, instance *Instance) error
+	Delete(ctx context.Context) error
+}
+
+type CreateInstance struct {
+	Name string `json:"name"`
+}

backend/v3/domain/invoke.go

@@ -0,0 +1,94 @@
+package domain
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/eventstore"
+)
+
+var defaultInvoker = newEventStoreInvoker(newTraceInvoker(nil))
+
+func Invoke(ctx context.Context, cmd Commander) error {
+	invoker := newEventStoreInvoker(newTraceInvoker(nil))
+	opts := &CommandOpts{
+		Invoker: invoker.collector,
+	}
+	return invoker.Invoke(ctx, cmd, opts)
+}
+
+type eventStoreInvoker struct {
+	collector *eventCollector
+}
+
+func newEventStoreInvoker(next Invoker) *eventStoreInvoker {
+	return &eventStoreInvoker{collector: &eventCollector{next: next}}
+}
+
+func (i *eventStoreInvoker) Invoke(ctx context.Context, command Commander, opts *CommandOpts) (err error) {
+	err = i.collector.Invoke(ctx, command, opts)
+	if err != nil {
+		return err
+	}
+	if len(i.collector.events) > 0 {
+		err = eventstore.Publish(ctx, i.collector.events, opts.DB)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+type eventCollector struct {
+	next   Invoker
+	events []*eventstore.Event
+}
+
+type eventer interface {
+	Events() []*eventstore.Event
+}
+
+func (i *eventCollector) Invoke(ctx context.Context, command Commander, opts *CommandOpts) (err error) {
+	if e, ok := command.(eventer); ok && len(e.Events()) > 0 {
+		// we need to ensure all commands are executed in the same transaction
+		close, err := opts.EnsureTx(ctx)
+		if err != nil {
+			return err
+		}
+		defer func() { err = close(ctx, err) }()
+
+		i.events = append(i.events, e.Events()...)
+	}
+	if i.next != nil {
+		err = i.next.Invoke(ctx, command, opts)
+	} else {
+		err = command.Execute(ctx, opts)
+	}
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+type traceInvoker struct {
+	next Invoker
+}
+
+func newTraceInvoker(next Invoker) *traceInvoker {
+	return &traceInvoker{next: next}
+}
+
+func (i *traceInvoker) Invoke(ctx context.Context, command Commander, opts *CommandOpts) (err error) {
+	ctx, span := tracer.Start(ctx, fmt.Sprintf("%T", command))
+	defer span.End()
+
+	if i.next != nil {
+		err = i.next.Invoke(ctx, command, opts)
+	} else {
+		err = command.Execute(ctx, opts)
+	}
+	if err != nil {
+		span.RecordError(err)
+	}
+	return err
+}

backend/v3/domain/org.go

@@ -0,0 +1,39 @@
+package domain
+
+import (
+	"context"
+	"time"
+)
+
+type Org struct {
+	ID   string `json:"id"`
+	Name string `json:"name"`
+
+	CreatedAt time.Time `json:"createdAt"`
+	UpdatedAt time.Time `json:"updatedAt"`
+}
+
+type OrgRepository interface {
+	ByID(ctx context.Context, orgID string) (*Org, error)
+	Create(ctx context.Context, org *Org) error
+	On(id string) OrgOperation
+}
+
+type OrgOperation interface {
+	AdminRepository
+	DomainRepository
+	Update(ctx context.Context, org *Org) error
+	Delete(ctx context.Context) error
+}
+
+type AdminRepository interface {
+	AddAdmin(ctx context.Context, userID string, roles []string) error
+	SetAdminRoles(ctx context.Context, userID string, roles []string) error
+	RemoveAdmin(ctx context.Context, userID string) error
+}
+
+type DomainRepository interface {
+	AddDomain(ctx context.Context, domain string) error
+	SetDomainVerified(ctx context.Context, domain string) error
+	RemoveDomain(ctx context.Context, domain string) error
+}

backend/v3/domain/org_add.go

@@ -0,0 +1,74 @@
+package domain
+
+import (
+	"context"
+)
+
+type AddOrgCommand struct {
+	ID     string            `json:"id"`
+	Name   string            `json:"name"`
+	Admins []AddAdminCommand `json:"admins"`
+}
+
+func NewAddOrgCommand(name string, admins ...AddAdminCommand) *AddOrgCommand {
+	return &AddOrgCommand{
+		Name:   name,
+		Admins: admins,
+	}
+}
+
+// Execute implements Commander.
+func (cmd *AddOrgCommand) Execute(ctx context.Context, opts *CommandOpts) (err error) {
+	if len(cmd.Admins) == 0 {
+		return ErrNoAdminSpecified
+	}
+	if err = cmd.ensureID(); err != nil {
+		return err
+	}
+
+	close, err := opts.EnsureTx(ctx)
+	if err != nil {
+		return err
+	}
+	defer func() { err = close(ctx, err) }()
+	err = orgRepo(opts.DB).Create(ctx, &Org{
+		ID:   cmd.ID,
+		Name: cmd.Name,
+	})
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+var (
+	_ Commander = (*AddOrgCommand)(nil)
+)
+
+func (cmd *AddOrgCommand) ensureID() (err error) {
+	if cmd.ID != "" {
+		return nil
+	}
+	cmd.ID, err = generateID()
+	return err
+}
+
+type AddAdminCommand struct {
+	UserID string   `json:"userId"`
+	Roles  []string `json:"roles"`
+}
+
+// Execute implements Commander.
+func (a *AddAdminCommand) Execute(ctx context.Context, opts *CommandOpts) (err error) {
+	close, err := opts.EnsureTx(ctx)
+	if err != nil {
+		return err
+	}
+	defer func() { err = close(ctx, err) }()
+	return nil
+}
+
+var (
+	_ Commander = (*AddAdminCommand)(nil)
+)

backend/v3/domain/repository.go

@@ -0,0 +1,82 @@
+package domain
+
+import (
+	"time"
+
+	"golang.org/x/exp/constraints"
+)
+
+type Operation interface {
+	// TextOperation |
+	// 	NumberOperation |
+	// 	BoolOperation
+
+	op()
+}
+
+type clause[F ~uint8, Op Operation] struct {
+	field F
+	op    Op
+}
+
+func (c *clause[F, Op]) Field() F {
+	return c.field
+}
+
+func (c *clause[F, Op]) Operation() Op {
+	return c.op
+}
+
+type Text interface {
+	~string | ~[]byte
+}
+
+type TextOperation uint8
+
+const (
+	TextOperationEqual TextOperation = iota
+	TextOperationNotEqual
+	TextOperationStartsWith
+	TextOperationStartsWithIgnoreCase
+)
+
+func (TextOperation) op() {}
+
+type Number interface {
+	constraints.Integer | constraints.Float | constraints.Complex | time.Time
+}
+
+type NumberOperation uint8
+
+const (
+	NumberOperationEqual NumberOperation = iota
+	NumberOperationNotEqual
+	NumberOperationLessThan
+	NumberOperationLessThanOrEqual
+	NumberOperationGreaterThan
+	NumberOperationGreaterThanOrEqual
+)
+
+func (NumberOperation) op() {}
+
+type Bool interface {
+	~bool
+}
+
+type BoolOperation uint8
+
+const (
+	BoolOperationIs BoolOperation = iota
+	BoolOperationNot
+)
+
+func (BoolOperation) op() {}
+
+type ListOperation uint8
+
+const (
+	ListOperationContains ListOperation = iota
+	ListOperationNotContains
+)
+
+func (ListOperation) op() {}

backend/v3/domain/set_email.go

@@ -0,0 +1,64 @@
+package domain
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/eventstore"
+)
+
+type SetEmailCommand struct {
+	UserID       string `json:"userId"`
+	Email        string `json:"email"`
+	verification Commander
+}
+
+var (
+	_ Commander      = (*SetEmailCommand)(nil)
+	_ eventer        = (*SetEmailCommand)(nil)
+	_ CreateHumanOpt = (*SetEmailCommand)(nil)
+)
+
+type SetEmailOpt interface {
+	applyOnSetEmail(*SetEmailCommand)
+}
+
+func NewSetEmailCommand(userID, email string, verificationType SetEmailOpt) *SetEmailCommand {
+	cmd := &SetEmailCommand{
+		UserID: userID,
+		Email:  email,
+	}
+	verificationType.applyOnSetEmail(cmd)
+	return cmd
+}
+
+func (cmd *SetEmailCommand) Execute(ctx context.Context, opts *CommandOpts) error {
+	close, err := opts.EnsureTx(ctx)
+	if err != nil {
+		return err
+	}
+	defer func() { err = close(ctx, err) }()
+	// userStatement(opts.DB).Human().ByID(cmd.UserID).SetEmail(ctx, cmd.Email)
+	err = userRepo(opts.DB).Human().ByID(cmd.UserID).Exec().SetEmail(ctx, cmd.Email)
+	if err != nil {
+		return err
+	}
+
+	return opts.Invoke(ctx, cmd.verification)
+}
+
+// Events implements [eventer].
+func (cmd *SetEmailCommand) Events() []*eventstore.Event {
+	return []*eventstore.Event{
+		{
+			AggregateType: "user",
+			AggregateID:   cmd.UserID,
+			Type:          "user.email.set",
+			Payload:       cmd,
+		},
+	}
+}
+
+// applyOnCreateHuman implements [CreateHumanOpt].
+func (cmd *SetEmailCommand) applyOnCreateHuman(createUserCmd *CreateUserCommand[Human]) {
+	createUserCmd.email = cmd
+}

backend/v3/domain/user.go

@@ -0,0 +1,193 @@
+package domain
+
+import (
+	"context"
+	"time"
+
+	v4 "github.com/zitadel/zitadel/backend/v3/storage/database/repository/stmt/v4"
+)
+
+type userColumns interface {
+	// TODO: move v4.columns to domain
+	InstanceIDColumn() column
+	OrgIDColumn() column
+	IDColumn() column
+	usernameColumn() column
+	CreatedAtColumn() column
+	UpdatedAtColumn() column
+	DeletedAtColumn() column
+}
+
+type userConditions interface {
+	InstanceIDCondition(instanceID string) v4.Condition
+	OrgIDCondition(orgID string) v4.Condition
+	IDCondition(userID string) v4.Condition
+	UsernameCondition(op v4.TextOperator, username string) v4.Condition
+	CreatedAtCondition(op v4.NumberOperator, createdAt time.Time) v4.Condition
+	UpdatedAtCondition(op v4.NumberOperator, updatedAt time.Time) v4.Condition
+	DeletedCondition(isDeleted bool) v4.Condition
+	DeletedAtCondition(op v4.NumberOperator, deletedAt time.Time) v4.Condition
+}
+
+type UserRepository interface {
+	userColumns
+	userConditions
+	// TODO: move condition to domain
+	WithCondition(condition v4.Condition) UserRepository
+	Get(ctx context.Context) (*User, error)
+	List(ctx context.Context) ([]*User, error)
+	Create(ctx context.Context, user *User) error
+	Delete(ctx context.Context) error
+
+	Human() HumanRepository
+	Machine() MachineRepository
+}
+
+type humanColumns interface {
+	FirstNameColumn() column
+	LastNameColumn() column
+	EmailAddressColumn() column
+	EmailVerifiedAtColumn() column
+	PhoneNumberColumn() column
+	PhoneVerifiedAtColumn() column
+}
+
+type humanConditions interface {
+	FirstNameCondition(op v4.TextOperator, firstName string) v4.Condition
+	LastNameCondition(op v4.TextOperator, lastName string) v4.Condition
+	EmailAddressCondition(op v4.TextOperator, email string) v4.Condition
+	EmailAddressVerifiedCondition(isVerified bool) v4.Condition
+	EmailVerifiedAtCondition(op v4.TextOperator, emailVerifiedAt string) v4.Condition
+	PhoneNumberCondition(op v4.TextOperator, phoneNumber string) v4.Condition
+	PhoneNumberVerifiedCondition(isVerified bool) v4.Condition
+	PhoneVerifiedAtCondition(op v4.TextOperator, phoneVerifiedAt string) v4.Condition
+}
+
+type HumanRepository interface {
+	humanColumns
+	humanConditions
+
+	GetEmail(ctx context.Context) (*Email, error)
+	// TODO: replace any with add email update columns
+	SetEmail(ctx context.Context, columns ...any) error
+}
+
+type machineColumns interface {
+	DescriptionColumn() column
+}
+
+type machineConditions interface {
+	DescriptionCondition(op v4.TextOperator, description string) v4.Condition
+}
+
+type MachineRepository interface {
+	machineColumns
+	machineConditions
+}
+
+// type UserRepository interface {
+// 	// Get(ctx context.Context, clauses ...UserClause) (*User, error)
+// 	// Search(ctx context.Context, clauses ...UserClause) ([]*User, error)
+
+// 	UserQuery[UserOperation]
+// 	Human() HumanQuery
+// 	Machine() MachineQuery
+// }
+
+// type UserQuery[Op UserOperation] interface {
+// 	ByID(id string) UserQuery[Op]
+// 	Username(username string) UserQuery[Op]
+// 	Exec() Op
+// }
+
+// type HumanQuery interface {
+// 	UserQuery[HumanOperation]
+// 	Email(op TextOperation, email string) HumanQuery
+// 	HumanOperation
+// }
+
+// type MachineQuery interface {
+// 	UserQuery[MachineOperation]
+// 	MachineOperation
+// }
+
+// type UserClause interface {
+// 	Field() UserField
+// 	Operation() Operation
+// 	Args() []any
+// }
+
+// type UserField uint8
+
+// const (
+// 	// Fields used for all users
+// 	UserFieldInstanceID UserField = iota + 1
+// 	UserFieldOrgID
+// 	UserFieldID
+// 	UserFieldUsername
+
+// 	// Fields used for human users
+// 	UserHumanFieldEmail
+// 	UserHumanFieldEmailVerified
+
+// 	// Fields used for machine users
+// 	UserMachineFieldDescription
+// )
+
+// type userByIDClause struct {
+// 	id string
+// }
+
+// func (c *userByIDClause) Field() UserField {
+// 	return UserFieldID
+// }
+
+// func (c *userByIDClause) Operation() Operation {
+// 	return TextOperationEqual
+// }
+
+// func (c *userByIDClause) Args() []any {
+// 	return []any{c.id}
+// }
+
+// type UserOperation interface {
+// 	Delete(ctx context.Context) error
+// 	SetUsername(ctx context.Context, username string) error
+// }
+
+// type HumanOperation interface {
+// 	UserOperation
+// 	SetEmail(ctx context.Context, email string) error
+// 	SetEmailVerified(ctx context.Context, email string) error
+// 	GetEmail(ctx context.Context) (*Email, error)
+// }
+
+// type MachineOperation interface {
+// 	UserOperation
+// 	SetDescription(ctx context.Context, description string) error
+// }
+
+type User struct {
+	v4.User
+}
+
+// type userTraits interface {
+// 	isUserTraits()
+// }
+
+// type Human struct {
+// 	Email *Email `json:"email"`
+// }
+
+// func (*Human) isUserTraits() {}
+
+// type Machine struct {
+// 	Description string `json:"description"`
+// }
+
+// func (*Machine) isUserTraits() {}
+
+// type Email struct {
+// 	Address    string `json:"address"`
+// 	IsVerified bool   `json:"isVerified"`
+// }

backend/v3/storage/cache/cache.go

@@ -0,0 +1,112 @@
+// Package cache provides abstraction of cache implementations that can be used by zitadel.
+package cache
+
+import (
+	"context"
+	"time"
+
+	"github.com/zitadel/logging"
+)
+
+// Purpose describes which object types are stored by a cache.
+type Purpose int
+
+//go:generate enumer -type Purpose -transform snake -trimprefix Purpose
+const (
+	PurposeUnspecified Purpose = iota
+	PurposeAuthzInstance
+	PurposeMilestones
+	PurposeOrganization
+	PurposeIdPFormCallback
+)
+
+// Cache stores objects with a value of type `V`.
+// Objects may be referred to by one or more indices.
+// Implementations may encode the value for storage.
+// This means non-exported fields may be lost and objects
+// with function values may fail to encode.
+// See https://pkg.go.dev/encoding/json#Marshal for example.
+//
+// `I` is the type by which indices are identified,
+// typically an enum for type-safe access.
+// Indices are defined when calling the constructor of an implementation of this interface.
+// It is illegal to refer to an idex not defined during construction.
+//
+// `K` is the type used as key in each index.
+// Due to the limitations in type constraints, all indices use the same key type.
+//
+// Implementations are free to use stricter type constraints or fixed typing.
+type Cache[I, K comparable, V Entry[I, K]] interface {
+	// Get an object through specified index.
+	// An [IndexUnknownError] may be returned if the index is unknown.
+	// [ErrCacheMiss] is returned if the key was not found in the index,
+	// or the object is not valid.
+	Get(ctx context.Context, index I, key K) (V, bool)
+
+	// Set an object.
+	// Keys are created on each index based in the [Entry.Keys] method.
+	// If any key maps to an existing object, the object is invalidated,
+	// regardless if the object has other keys defined in the new entry.
+	// This to prevent ghost objects when an entry reduces the amount of keys
+	// for a given index.
+	Set(ctx context.Context, value V)
+
+	// Invalidate an object through specified index.
+	// Implementations may choose to instantly delete the object,
+	// defer until prune or a separate cleanup routine.
+	// Invalidated object are no longer returned from Get.
+	// It is safe to call Invalidate multiple times or on non-existing entries.
+	Invalidate(ctx context.Context, index I, key ...K) error
+
+	// Delete one or more keys from a specific index.
+	// An [IndexUnknownError] may be returned if the index is unknown.
+	// The referred object is not invalidated and may still be accessible though
+	// other indices and keys.
+	// It is safe to call Delete multiple times or on non-existing entries
+	Delete(ctx context.Context, index I, key ...K) error
+
+	// Truncate deletes all cached objects.
+	Truncate(ctx context.Context) error
+}
+
+// Entry contains a value of type `V` to be cached.
+//
+// `I` is the type by which indices are identified,
+// typically an enum for type-safe access.
+//
+// `K` is the type used as key in an index.
+// Due to the limitations in type constraints, all indices use the same key type.
+type Entry[I, K comparable] interface {
+	// Keys returns which keys map to the object in a specified index.
+	// May return nil if the index in unknown or when there are no keys.
+	Keys(index I) (key []K)
+}
+
+type Connector int
+
+//go:generate enumer -type Connector -transform snake -trimprefix Connector -linecomment -text
+const (
+	// Empty line comment ensures empty string for unspecified value
+	ConnectorUnspecified Connector = iota //
+	ConnectorMemory
+	ConnectorPostgres
+	ConnectorRedis
+)
+
+type Config struct {
+	Connector Connector
+
+	// Age since an object was added to the cache,
+	// after which the object is considered invalid.
+	// 0 disables max age checks.
+	MaxAge time.Duration
+
+	// Age since last use (Get) of an object,
+	// after which the object is considered invalid.
+	// 0 disables last use age checks.
+	LastUseAge time.Duration
+
+	// Log allows logging of the specific cache.
+	// By default only errors are logged to stdout.
+	Log *logging.Config
+}

backend/v3/storage/cache/connector/connector.go

@@ -0,0 +1,49 @@
+// Package connector provides glue between the [cache.Cache] interface and implementations from the connector sub-packages.
+package connector
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/cache"
+	"github.com/zitadel/zitadel/backend/v3/storage/cache/connector/gomap"
+	"github.com/zitadel/zitadel/backend/v3/storage/cache/connector/noop"
+)
+
+type CachesConfig struct {
+	Connectors struct {
+		Memory gomap.Config
+	}
+	Instance         *cache.Config
+	Milestones       *cache.Config
+	Organization     *cache.Config
+	IdPFormCallbacks *cache.Config
+}
+
+type Connectors struct {
+	Config CachesConfig
+	Memory *gomap.Connector
+}
+
+func StartConnectors(conf *CachesConfig) (Connectors, error) {
+	if conf == nil {
+		return Connectors{}, nil
+	}
+	return Connectors{
+		Config: *conf,
+		Memory: gomap.NewConnector(conf.Connectors.Memory),
+	}, nil
+}
+
+func StartCache[I ~int, K ~string, V cache.Entry[I, K]](background context.Context, indices []I, purpose cache.Purpose, conf *cache.Config, connectors Connectors) (cache.Cache[I, K, V], error) {
+	if conf == nil || conf.Connector == cache.ConnectorUnspecified {
+		return noop.NewCache[I, K, V](), nil
+	}
+	if conf.Connector == cache.ConnectorMemory && connectors.Memory != nil {
+		c := gomap.NewCache[I, K, V](background, indices, *conf)
+		connectors.Memory.Config.StartAutoPrune(background, c, purpose)
+		return c, nil
+	}
+
+	return nil, fmt.Errorf("cache connector %q not enabled", conf.Connector)
+}

backend/v3/storage/cache/connector/gomap/connector.go

@@ -0,0 +1,23 @@
+package gomap
+
+import (
+	"github.com/zitadel/zitadel/backend/v3/storage/cache"
+)
+
+type Config struct {
+	Enabled   bool
+	AutoPrune cache.AutoPruneConfig
+}
+
+type Connector struct {
+	Config cache.AutoPruneConfig
+}
+
+func NewConnector(config Config) *Connector {
+	if !config.Enabled {
+		return nil
+	}
+	return &Connector{
+		Config: config.AutoPrune,
+	}
+}

backend/v3/storage/cache/connector/gomap/gomap.go

@@ -0,0 +1,200 @@
+package gomap
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+	"maps"
+	"os"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/cache"
+)
+
+type mapCache[I, K comparable, V cache.Entry[I, K]] struct {
+	config   *cache.Config
+	indexMap map[I]*index[K, V]
+	logger   *slog.Logger
+}
+
+// NewCache returns an in-memory Cache implementation based on the builtin go map type.
+// Object values are stored as-is and there is no encoding or decoding involved.
+func NewCache[I, K comparable, V cache.Entry[I, K]](background context.Context, indices []I, config cache.Config) cache.PrunerCache[I, K, V] {
+	m := &mapCache[I, K, V]{
+		config:   &config,
+		indexMap: make(map[I]*index[K, V], len(indices)),
+		logger: slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{
+			AddSource: true,
+			Level:     slog.LevelError,
+		})),
+	}
+	if config.Log != nil {
+		m.logger = config.Log.Slog()
+	}
+	m.logger.InfoContext(background, "map cache logging enabled")
+
+	for _, name := range indices {
+		m.indexMap[name] = &index[K, V]{
+			config:  m.config,
+			entries: make(map[K]*entry[V]),
+		}
+	}
+	return m
+}
+
+func (c *mapCache[I, K, V]) Get(ctx context.Context, index I, key K) (value V, ok bool) {
+	i, ok := c.indexMap[index]
+	if !ok {
+		c.logger.ErrorContext(ctx, "map cache get", "err", cache.NewIndexUnknownErr(index), "index", index, "key", key)
+		return value, false
+	}
+	entry, err := i.Get(key)
+	if err == nil {
+		c.logger.DebugContext(ctx, "map cache get", "index", index, "key", key)
+		return entry.value, true
+	}
+	if errors.Is(err, cache.ErrCacheMiss) {
+		c.logger.InfoContext(ctx, "map cache get", "err", err, "index", index, "key", key)
+		return value, false
+	}
+	c.logger.ErrorContext(ctx, "map cache get", "err", cache.NewIndexUnknownErr(index), "index", index, "key", key)
+	return value, false
+}
+
+func (c *mapCache[I, K, V]) Set(ctx context.Context, value V) {
+	now := time.Now()
+	entry := &entry[V]{
+		value:   value,
+		created: now,
+	}
+	entry.lastUse.Store(now.UnixMicro())
+
+	for name, i := range c.indexMap {
+		keys := value.Keys(name)
+		i.Set(keys, entry)
+		c.logger.DebugContext(ctx, "map cache set", "index", name, "keys", keys)
+	}
+}
+
+func (c *mapCache[I, K, V]) Invalidate(ctx context.Context, index I, keys ...K) error {
+	i, ok := c.indexMap[index]
+	if !ok {
+		return cache.NewIndexUnknownErr(index)
+	}
+	i.Invalidate(keys)
+	c.logger.DebugContext(ctx, "map cache invalidate", "index", index, "keys", keys)
+	return nil
+}
+
+func (c *mapCache[I, K, V]) Delete(ctx context.Context, index I, keys ...K) error {
+	i, ok := c.indexMap[index]
+	if !ok {
+		return cache.NewIndexUnknownErr(index)
+	}
+	i.Delete(keys)
+	c.logger.DebugContext(ctx, "map cache delete", "index", index, "keys", keys)
+	return nil
+}
+
+func (c *mapCache[I, K, V]) Prune(ctx context.Context) error {
+	for name, index := range c.indexMap {
+		index.Prune()
+		c.logger.DebugContext(ctx, "map cache prune", "index", name)
+	}
+	return nil
+}
+
+func (c *mapCache[I, K, V]) Truncate(ctx context.Context) error {
+	for name, index := range c.indexMap {
+		index.Truncate()
+		c.logger.DebugContext(ctx, "map cache truncate", "index", name)
+	}
+	return nil
+}
+
+type index[K comparable, V any] struct {
+	mutex   sync.RWMutex
+	config  *cache.Config
+	entries map[K]*entry[V]
+}
+
+func (i *index[K, V]) Get(key K) (*entry[V], error) {
+	i.mutex.RLock()
+	entry, ok := i.entries[key]
+	i.mutex.RUnlock()
+	if ok && entry.isValid(i.config) {
+		return entry, nil
+	}
+	return nil, cache.ErrCacheMiss
+}
+
+func (c *index[K, V]) Set(keys []K, entry *entry[V]) {
+	c.mutex.Lock()
+	for _, key := range keys {
+		c.entries[key] = entry
+	}
+	c.mutex.Unlock()
+}
+
+func (i *index[K, V]) Invalidate(keys []K) {
+	i.mutex.RLock()
+	for _, key := range keys {
+		if entry, ok := i.entries[key]; ok {
+			entry.invalid.Store(true)
+		}
+	}
+	i.mutex.RUnlock()
+}
+
+func (c *index[K, V]) Delete(keys []K) {
+	c.mutex.Lock()
+	for _, key := range keys {
+		delete(c.entries, key)
+	}
+	c.mutex.Unlock()
+}
+
+func (c *index[K, V]) Prune() {
+	c.mutex.Lock()
+	maps.DeleteFunc(c.entries, func(_ K, entry *entry[V]) bool {
+		return !entry.isValid(c.config)
+	})
+	c.mutex.Unlock()
+}
+
+func (c *index[K, V]) Truncate() {
+	c.mutex.Lock()
+	c.entries = make(map[K]*entry[V])
+	c.mutex.Unlock()
+}
+
+type entry[V any] struct {
+	value   V
+	created time.Time
+	invalid atomic.Bool
+	lastUse atomic.Int64 // UnixMicro time
+}
+
+func (e *entry[V]) isValid(c *cache.Config) bool {
+	if e.invalid.Load() {
+		return false
+	}
+	now := time.Now()
+	if c.MaxAge > 0 {
+		if e.created.Add(c.MaxAge).Before(now) {
+			e.invalid.Store(true)
+			return false
+		}
+	}
+	if c.LastUseAge > 0 {
+		lastUse := e.lastUse.Load()
+		if time.UnixMicro(lastUse).Add(c.LastUseAge).Before(now) {
+			e.invalid.Store(true)
+			return false
+		}
+		e.lastUse.CompareAndSwap(lastUse, now.UnixMicro())
+	}
+	return true
+}

backend/v3/storage/cache/connector/gomap/gomap_test.go

@@ -0,0 +1,329 @@
+package gomap
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/zitadel/logging"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/cache"
+)
+
+type testIndex int
+
+const (
+	testIndexID testIndex = iota
+	testIndexName
+)
+
+var testIndices = []testIndex{
+	testIndexID,
+	testIndexName,
+}
+
+type testObject struct {
+	id    string
+	names []string
+}
+
+func (o *testObject) Keys(index testIndex) []string {
+	switch index {
+	case testIndexID:
+		return []string{o.id}
+	case testIndexName:
+		return o.names
+	default:
+		return nil
+	}
+}
+
+func Test_mapCache_Get(t *testing.T) {
+	c := NewCache[testIndex, string, *testObject](context.Background(), testIndices, cache.Config{
+		MaxAge:     time.Second,
+		LastUseAge: time.Second / 4,
+		Log: &logging.Config{
+			Level:     "debug",
+			AddSource: true,
+		},
+	})
+	obj := &testObject{
+		id:    "id",
+		names: []string{"foo", "bar"},
+	}
+	c.Set(context.Background(), obj)
+
+	type args struct {
+		index testIndex
+		key   string
+	}
+	tests := []struct {
+		name   string
+		args   args
+		want   *testObject
+		wantOk bool
+	}{
+		{
+			name: "ok",
+			args: args{
+				index: testIndexID,
+				key:   "id",
+			},
+			want:   obj,
+			wantOk: true,
+		},
+		{
+			name: "miss",
+			args: args{
+				index: testIndexID,
+				key:   "spanac",
+			},
+			want:   nil,
+			wantOk: false,
+		},
+		{
+			name: "unknown index",
+			args: args{
+				index: 99,
+				key:   "id",
+			},
+			want:   nil,
+			wantOk: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, ok := c.Get(context.Background(), tt.args.index, tt.args.key)
+			assert.Equal(t, tt.want, got)
+			assert.Equal(t, tt.wantOk, ok)
+		})
+	}
+}
+
+func Test_mapCache_Invalidate(t *testing.T) {
+	c := NewCache[testIndex, string, *testObject](context.Background(), testIndices, cache.Config{
+		MaxAge:     time.Second,
+		LastUseAge: time.Second / 4,
+		Log: &logging.Config{
+			Level:     "debug",
+			AddSource: true,
+		},
+	})
+	obj := &testObject{
+		id:    "id",
+		names: []string{"foo", "bar"},
+	}
+	c.Set(context.Background(), obj)
+	err := c.Invalidate(context.Background(), testIndexName, "bar")
+	require.NoError(t, err)
+	got, ok := c.Get(context.Background(), testIndexID, "id")
+	assert.Nil(t, got)
+	assert.False(t, ok)
+}
+
+func Test_mapCache_Delete(t *testing.T) {
+	c := NewCache[testIndex, string, *testObject](context.Background(), testIndices, cache.Config{
+		MaxAge:     time.Second,
+		LastUseAge: time.Second / 4,
+		Log: &logging.Config{
+			Level:     "debug",
+			AddSource: true,
+		},
+	})
+	obj := &testObject{
+		id:    "id",
+		names: []string{"foo", "bar"},
+	}
+	c.Set(context.Background(), obj)
+	err := c.Delete(context.Background(), testIndexName, "bar")
+	require.NoError(t, err)
+
+	// Shouldn't find object by deleted name
+	got, ok := c.Get(context.Background(), testIndexName, "bar")
+	assert.Nil(t, got)
+	assert.False(t, ok)
+
+	// Should find object by other name
+	got, ok = c.Get(context.Background(), testIndexName, "foo")
+	assert.Equal(t, obj, got)
+	assert.True(t, ok)
+
+	// Should find object by id
+	got, ok = c.Get(context.Background(), testIndexID, "id")
+	assert.Equal(t, obj, got)
+	assert.True(t, ok)
+}
+
+func Test_mapCache_Prune(t *testing.T) {
+	c := NewCache[testIndex, string, *testObject](context.Background(), testIndices, cache.Config{
+		MaxAge:     time.Second,
+		LastUseAge: time.Second / 4,
+		Log: &logging.Config{
+			Level:     "debug",
+			AddSource: true,
+		},
+	})
+
+	objects := []*testObject{
+		{
+			id:    "id1",
+			names: []string{"foo", "bar"},
+		},
+		{
+			id:    "id2",
+			names: []string{"hello"},
+		},
+	}
+	for _, obj := range objects {
+		c.Set(context.Background(), obj)
+	}
+	// invalidate one entry
+	err := c.Invalidate(context.Background(), testIndexName, "bar")
+	require.NoError(t, err)
+
+	err = c.(cache.Pruner).Prune(context.Background())
+	require.NoError(t, err)
+
+	// Other object should still be found
+	got, ok := c.Get(context.Background(), testIndexID, "id2")
+	assert.Equal(t, objects[1], got)
+	assert.True(t, ok)
+}
+
+func Test_mapCache_Truncate(t *testing.T) {
+	c := NewCache[testIndex, string, *testObject](context.Background(), testIndices, cache.Config{
+		MaxAge:     time.Second,
+		LastUseAge: time.Second / 4,
+		Log: &logging.Config{
+			Level:     "debug",
+			AddSource: true,
+		},
+	})
+	objects := []*testObject{
+		{
+			id:    "id1",
+			names: []string{"foo", "bar"},
+		},
+		{
+			id:    "id2",
+			names: []string{"hello"},
+		},
+	}
+	for _, obj := range objects {
+		c.Set(context.Background(), obj)
+	}
+
+	err := c.Truncate(context.Background())
+	require.NoError(t, err)
+
+	mc := c.(*mapCache[testIndex, string, *testObject])
+	for _, index := range mc.indexMap {
+		index.mutex.RLock()
+		assert.Len(t, index.entries, 0)
+		index.mutex.RUnlock()
+	}
+}
+
+func Test_entry_isValid(t *testing.T) {
+	type fields struct {
+		created time.Time
+		invalid bool
+		lastUse time.Time
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		config *cache.Config
+		want   bool
+	}{
+		{
+			name: "invalid",
+			fields: fields{
+				created: time.Now(),
+				invalid: true,
+				lastUse: time.Now(),
+			},
+			config: &cache.Config{
+				MaxAge:     time.Minute,
+				LastUseAge: time.Second,
+			},
+			want: false,
+		},
+		{
+			name: "max age exceeded",
+			fields: fields{
+				created: time.Now().Add(-(time.Minute + time.Second)),
+				invalid: false,
+				lastUse: time.Now(),
+			},
+			config: &cache.Config{
+				MaxAge:     time.Minute,
+				LastUseAge: time.Second,
+			},
+			want: false,
+		},
+		{
+			name: "max age disabled",
+			fields: fields{
+				created: time.Now().Add(-(time.Minute + time.Second)),
+				invalid: false,
+				lastUse: time.Now(),
+			},
+			config: &cache.Config{
+				LastUseAge: time.Second,
+			},
+			want: true,
+		},
+		{
+			name: "last use age exceeded",
+			fields: fields{
+				created: time.Now().Add(-(time.Minute / 2)),
+				invalid: false,
+				lastUse: time.Now().Add(-(time.Second * 2)),
+			},
+			config: &cache.Config{
+				MaxAge:     time.Minute,
+				LastUseAge: time.Second,
+			},
+			want: false,
+		},
+		{
+			name: "last use age disabled",
+			fields: fields{
+				created: time.Now().Add(-(time.Minute / 2)),
+				invalid: false,
+				lastUse: time.Now().Add(-(time.Second * 2)),
+			},
+			config: &cache.Config{
+				MaxAge: time.Minute,
+			},
+			want: true,
+		},
+		{
+			name: "valid",
+			fields: fields{
+				created: time.Now(),
+				invalid: false,
+				lastUse: time.Now(),
+			},
+			config: &cache.Config{
+				MaxAge:     time.Minute,
+				LastUseAge: time.Second,
+			},
+			want: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			e := &entry[any]{
+				created: tt.fields.created,
+			}
+			e.invalid.Store(tt.fields.invalid)
+			e.lastUse.Store(tt.fields.lastUse.UnixMicro())
+			got := e.isValid(tt.config)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}

backend/v3/storage/cache/connector/noop/noop.go

@@ -0,0 +1,21 @@
+package noop
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/cache"
+)
+
+type noop[I, K comparable, V cache.Entry[I, K]] struct{}
+
+// NewCache returns a cache that does nothing
+func NewCache[I, K comparable, V cache.Entry[I, K]]() cache.Cache[I, K, V] {
+	return noop[I, K, V]{}
+}
+
+func (noop[I, K, V]) Set(context.Context, V)                          {}
+func (noop[I, K, V]) Get(context.Context, I, K) (value V, ok bool)    { return }
+func (noop[I, K, V]) Invalidate(context.Context, I, ...K) (err error) { return }
+func (noop[I, K, V]) Delete(context.Context, I, ...K) (err error)     { return }
+func (noop[I, K, V]) Prune(context.Context) (err error)               { return }
+func (noop[I, K, V]) Truncate(context.Context) (err error)            { return }

backend/v3/storage/cache/connector_enumer.go

@@ -0,0 +1,98 @@
+// Code generated by "enumer -type Connector -transform snake -trimprefix Connector -linecomment -text"; DO NOT EDIT.
+
+package cache
+
+import (
+	"fmt"
+	"strings"
+)
+
+const _ConnectorName = "memorypostgresredis"
+
+var _ConnectorIndex = [...]uint8{0, 0, 6, 14, 19}
+
+const _ConnectorLowerName = "memorypostgresredis"
+
+func (i Connector) String() string {
+	if i < 0 || i >= Connector(len(_ConnectorIndex)-1) {
+		return fmt.Sprintf("Connector(%d)", i)
+	}
+	return _ConnectorName[_ConnectorIndex[i]:_ConnectorIndex[i+1]]
+}
+
+// An "invalid array index" compiler error signifies that the constant values have changed.
+// Re-run the stringer command to generate them again.
+func _ConnectorNoOp() {
+	var x [1]struct{}
+	_ = x[ConnectorUnspecified-(0)]
+	_ = x[ConnectorMemory-(1)]
+	_ = x[ConnectorPostgres-(2)]
+	_ = x[ConnectorRedis-(3)]
+}
+
+var _ConnectorValues = []Connector{ConnectorUnspecified, ConnectorMemory, ConnectorPostgres, ConnectorRedis}
+
+var _ConnectorNameToValueMap = map[string]Connector{
+	_ConnectorName[0:0]:        ConnectorUnspecified,
+	_ConnectorLowerName[0:0]:   ConnectorUnspecified,
+	_ConnectorName[0:6]:        ConnectorMemory,
+	_ConnectorLowerName[0:6]:   ConnectorMemory,
+	_ConnectorName[6:14]:       ConnectorPostgres,
+	_ConnectorLowerName[6:14]:  ConnectorPostgres,
+	_ConnectorName[14:19]:      ConnectorRedis,
+	_ConnectorLowerName[14:19]: ConnectorRedis,
+}
+
+var _ConnectorNames = []string{
+	_ConnectorName[0:0],
+	_ConnectorName[0:6],
+	_ConnectorName[6:14],
+	_ConnectorName[14:19],
+}
+
+// ConnectorString retrieves an enum value from the enum constants string name.
+// Throws an error if the param is not part of the enum.
+func ConnectorString(s string) (Connector, error) {
+	if val, ok := _ConnectorNameToValueMap[s]; ok {
+		return val, nil
+	}
+
+	if val, ok := _ConnectorNameToValueMap[strings.ToLower(s)]; ok {
+		return val, nil
+	}
+	return 0, fmt.Errorf("%s does not belong to Connector values", s)
+}
+
+// ConnectorValues returns all values of the enum
+func ConnectorValues() []Connector {
+	return _ConnectorValues
+}
+
+// ConnectorStrings returns a slice of all String values of the enum
+func ConnectorStrings() []string {
+	strs := make([]string, len(_ConnectorNames))
+	copy(strs, _ConnectorNames)
+	return strs
+}
+
+// IsAConnector returns "true" if the value is listed in the enum definition. "false" otherwise
+func (i Connector) IsAConnector() bool {
+	for _, v := range _ConnectorValues {
+		if i == v {
+			return true
+		}
+	}
+	return false
+}
+
+// MarshalText implements the encoding.TextMarshaler interface for Connector
+func (i Connector) MarshalText() ([]byte, error) {
+	return []byte(i.String()), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface for Connector
+func (i *Connector) UnmarshalText(text []byte) error {
+	var err error
+	*i, err = ConnectorString(string(text))
+	return err
+}

backend/v3/storage/cache/error.go

@@ -0,0 +1,29 @@
+package cache
+
+import (
+	"errors"
+	"fmt"
+)
+
+type IndexUnknownError[I comparable] struct {
+	index I
+}
+
+func NewIndexUnknownErr[I comparable](index I) error {
+	return IndexUnknownError[I]{index}
+}
+
+func (i IndexUnknownError[I]) Error() string {
+	return fmt.Sprintf("index %v unknown", i.index)
+}
+
+func (a IndexUnknownError[I]) Is(err error) bool {
+	if b, ok := err.(IndexUnknownError[I]); ok {
+		return a.index == b.index
+	}
+	return false
+}
+
+var (
+	ErrCacheMiss = errors.New("cache miss")
+)

backend/v3/storage/cache/pruner.go

@@ -0,0 +1,76 @@
+package cache
+
+import (
+	"context"
+	"math/rand"
+	"time"
+
+	"github.com/jonboulle/clockwork"
+	"github.com/zitadel/logging"
+)
+
+// Pruner is an optional [Cache] interface.
+type Pruner interface {
+	// Prune deletes all invalidated or expired objects.
+	Prune(ctx context.Context) error
+}
+
+type PrunerCache[I, K comparable, V Entry[I, K]] interface {
+	Cache[I, K, V]
+	Pruner
+}
+
+type AutoPruneConfig struct {
+	// Interval at which the cache is automatically pruned.
+	// 0 or lower disables automatic pruning.
+	Interval time.Duration
+
+	// Timeout for an automatic prune.
+	// It is recommended to keep the value shorter than AutoPruneInterval
+	// 0 or lower disables automatic pruning.
+	Timeout time.Duration
+}
+
+func (c AutoPruneConfig) StartAutoPrune(background context.Context, pruner Pruner, purpose Purpose) (close func()) {
+	return c.startAutoPrune(background, pruner, purpose, clockwork.NewRealClock())
+}
+
+func (c *AutoPruneConfig) startAutoPrune(background context.Context, pruner Pruner, purpose Purpose, clock clockwork.Clock) (close func()) {
+	if c.Interval <= 0 {
+		return func() {}
+	}
+	background, cancel := context.WithCancel(background)
+	// randomize the first interval
+	timer := clock.NewTimer(time.Duration(rand.Int63n(int64(c.Interval))))
+	go c.pruneTimer(background, pruner, purpose, timer)
+	return cancel
+}
+
+func (c *AutoPruneConfig) pruneTimer(background context.Context, pruner Pruner, purpose Purpose, timer clockwork.Timer) {
+	defer func() {
+		if !timer.Stop() {
+			<-timer.Chan()
+		}
+	}()
+
+	for {
+		select {
+		case <-background.Done():
+			return
+		case <-timer.Chan():
+			err := c.doPrune(background, pruner)
+			logging.OnError(err).WithField("purpose", purpose).Error("cache auto prune")
+			timer.Reset(c.Interval)
+		}
+	}
+}
+
+func (c *AutoPruneConfig) doPrune(background context.Context, pruner Pruner) error {
+	ctx, cancel := context.WithCancel(background)
+	defer cancel()
+	if c.Timeout > 0 {
+		ctx, cancel = context.WithTimeout(background, c.Timeout)
+		defer cancel()
+	}
+	return pruner.Prune(ctx)
+}

backend/v3/storage/cache/pruner_test.go

@@ -0,0 +1,43 @@
+package cache
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/jonboulle/clockwork"
+	"github.com/stretchr/testify/assert"
+)
+
+type testPruner struct {
+	called chan struct{}
+}
+
+func (p *testPruner) Prune(context.Context) error {
+	p.called <- struct{}{}
+	return nil
+}
+
+func TestAutoPruneConfig_startAutoPrune(t *testing.T) {
+	c := AutoPruneConfig{
+		Interval: time.Second,
+		Timeout:  time.Millisecond,
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	pruner := testPruner{
+		called: make(chan struct{}),
+	}
+	clock := clockwork.NewFakeClock()
+	close := c.startAutoPrune(ctx, &pruner, PurposeAuthzInstance, clock)
+	defer close()
+	clock.Advance(time.Second)
+
+	select {
+	case _, ok := <-pruner.called:
+		assert.True(t, ok)
+	case <-ctx.Done():
+		t.Fatal(ctx.Err())
+	}
+}

backend/v3/storage/cache/purpose_enumer.go

@@ -0,0 +1,90 @@
+// Code generated by "enumer -type Purpose -transform snake -trimprefix Purpose"; DO NOT EDIT.
+
+package cache
+
+import (
+	"fmt"
+	"strings"
+)
+
+const _PurposeName = "unspecifiedauthz_instancemilestonesorganizationid_p_form_callback"
+
+var _PurposeIndex = [...]uint8{0, 11, 25, 35, 47, 65}
+
+const _PurposeLowerName = "unspecifiedauthz_instancemilestonesorganizationid_p_form_callback"
+
+func (i Purpose) String() string {
+	if i < 0 || i >= Purpose(len(_PurposeIndex)-1) {
+		return fmt.Sprintf("Purpose(%d)", i)
+	}
+	return _PurposeName[_PurposeIndex[i]:_PurposeIndex[i+1]]
+}
+
+// An "invalid array index" compiler error signifies that the constant values have changed.
+// Re-run the stringer command to generate them again.
+func _PurposeNoOp() {
+	var x [1]struct{}
+	_ = x[PurposeUnspecified-(0)]
+	_ = x[PurposeAuthzInstance-(1)]
+	_ = x[PurposeMilestones-(2)]
+	_ = x[PurposeOrganization-(3)]
+	_ = x[PurposeIdPFormCallback-(4)]
+}
+
+var _PurposeValues = []Purpose{PurposeUnspecified, PurposeAuthzInstance, PurposeMilestones, PurposeOrganization, PurposeIdPFormCallback}
+
+var _PurposeNameToValueMap = map[string]Purpose{
+	_PurposeName[0:11]:       PurposeUnspecified,
+	_PurposeLowerName[0:11]:  PurposeUnspecified,
+	_PurposeName[11:25]:      PurposeAuthzInstance,
+	_PurposeLowerName[11:25]: PurposeAuthzInstance,
+	_PurposeName[25:35]:      PurposeMilestones,
+	_PurposeLowerName[25:35]: PurposeMilestones,
+	_PurposeName[35:47]:      PurposeOrganization,
+	_PurposeLowerName[35:47]: PurposeOrganization,
+	_PurposeName[47:65]:      PurposeIdPFormCallback,
+	_PurposeLowerName[47:65]: PurposeIdPFormCallback,
+}
+
+var _PurposeNames = []string{
+	_PurposeName[0:11],
+	_PurposeName[11:25],
+	_PurposeName[25:35],
+	_PurposeName[35:47],
+	_PurposeName[47:65],
+}
+
+// PurposeString retrieves an enum value from the enum constants string name.
+// Throws an error if the param is not part of the enum.
+func PurposeString(s string) (Purpose, error) {
+	if val, ok := _PurposeNameToValueMap[s]; ok {
+		return val, nil
+	}
+
+	if val, ok := _PurposeNameToValueMap[strings.ToLower(s)]; ok {
+		return val, nil
+	}
+	return 0, fmt.Errorf("%s does not belong to Purpose values", s)
+}
+
+// PurposeValues returns all values of the enum
+func PurposeValues() []Purpose {
+	return _PurposeValues
+}
+
+// PurposeStrings returns a slice of all String values of the enum
+func PurposeStrings() []string {
+	strs := make([]string, len(_PurposeNames))
+	copy(strs, _PurposeNames)
+	return strs
+}
+
+// IsAPurpose returns "true" if the value is listed in the enum definition. "false" otherwise
+func (i Purpose) IsAPurpose() bool {
+	for _, v := range _PurposeValues {
+		if i == v {
+			return true
+		}
+	}
+	return false
+}

backend/v3/storage/database/config.go

@@ -0,0 +1,9 @@
+package database
+
+import (
+	"context"
+)
+
+type Connector interface {
+	Connect(ctx context.Context) (Pool, error)
+}

backend/v3/storage/database/database.go

@@ -0,0 +1,60 @@
+package database
+
+import (
+	"context"
+)
+
+var (
+	db *database
+)
+
+type database struct {
+	connector Connector
+	pool      Pool
+}
+
+type Pool interface {
+	Beginner
+	QueryExecutor
+
+	Acquire(ctx context.Context) (Client, error)
+	Close(ctx context.Context) error
+}
+
+type Client interface {
+	Beginner
+	QueryExecutor
+
+	Release(ctx context.Context) error
+}
+
+type Querier interface {
+	Query(ctx context.Context, stmt string, args ...any) (Rows, error)
+	QueryRow(ctx context.Context, stmt string, args ...any) Row
+}
+
+type Executor interface {
+	Exec(ctx context.Context, stmt string, args ...any) error
+}
+
+type QueryExecutor interface {
+	Querier
+	Executor
+}
+
+type Scanner interface {
+	Scan(dest ...any) error
+}
+
+type Row interface {
+	Scanner
+}
+
+type Rows interface {
+	Row
+	Next() bool
+	Close() error
+	Err() error
+}
+
+type Query[T any] func(querier Querier) (result T, err error)

backend/v3/storage/database/dialect/config.go

@@ -0,0 +1,92 @@
+package dialect
+
+import (
+	"context"
+	"errors"
+	"reflect"
+
+	"github.com/mitchellh/mapstructure"
+	"github.com/spf13/viper"
+
+	"github.com/zitadel/zitadel/backend/storage/database"
+	"github.com/zitadel/zitadel/backend/storage/database/dialect/postgres"
+)
+
+type Hook struct {
+	Match       func(string) bool
+	Decode      func(config any) (database.Connector, error)
+	Name        string
+	Constructor func() database.Connector
+}
+
+var hooks = []Hook{
+	{
+		Match:       postgres.NameMatcher,
+		Decode:      postgres.DecodeConfig,
+		Name:        postgres.Name,
+		Constructor: func() database.Connector { return new(postgres.Config) },
+	},
+	// {
+	// 	Match:       gosql.NameMatcher,
+	// 	Decode:      gosql.DecodeConfig,
+	// 	Name:        gosql.Name,
+	// 	Constructor: func() database.Connector { return new(gosql.Config) },
+	// },
+}
+
+type Config struct {
+	Dialects map[string]any `mapstructure:",remain" yaml:",inline"`
+
+	connector database.Connector
+}
+
+func (c Config) Connect(ctx context.Context) (database.Pool, error) {
+	if len(c.Dialects) != 1 {
+		return nil, errors.New("Exactly one dialect must be configured")
+	}
+
+	return c.connector.Connect(ctx)
+}
+
+// Hooks implements [configure.Unmarshaller].
+func (c Config) Hooks() []viper.DecoderConfigOption {
+	return []viper.DecoderConfigOption{
+		viper.DecodeHook(decodeHook),
+	}
+}
+
+func decodeHook(from, to reflect.Value) (_ any, err error) {
+	if to.Type() != reflect.TypeOf(Config{}) {
+		return from.Interface(), nil
+	}
+
+	config := new(Config)
+	if err = mapstructure.Decode(from.Interface(), config); err != nil {
+		return nil, err
+	}
+
+	if err = config.decodeDialect(); err != nil {
+		return nil, err
+	}
+
+	return config, nil
+}
+
+func (c *Config) decodeDialect() error {
+	for _, hook := range hooks {
+		for name, config := range c.Dialects {
+			if !hook.Match(name) {
+				continue
+			}
+
+			connector, err := hook.Decode(config)
+			if err != nil {
+				return err
+			}
+
+			c.connector = connector
+			return nil
+		}
+	}
+	return errors.New("no dialect found")
+}

backend/v3/storage/database/dialect/postgres/config.go

@@ -0,0 +1,80 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"slices"
+	"strings"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+	"github.com/mitchellh/mapstructure"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+var (
+	_    database.Connector = (*Config)(nil)
+	Name                    = "postgres"
+)
+
+type Config struct {
+	*pgxpool.Config
+
+	// Host               string
+	// Port               int32
+	// Database           string
+	// MaxOpenConns       uint32
+	// MaxIdleConns       uint32
+	// MaxConnLifetime    time.Duration
+	// MaxConnIdleTime    time.Duration
+	// User               User
+	// // Additional options to be appended as options=<Options>
+	// // The value will be taken as is. Multiple options are space separated.
+	// Options string
+
+	configuredFields []string
+}
+
+// Connect implements [database.Connector].
+func (c *Config) Connect(ctx context.Context) (database.Pool, error) {
+	pool, err := pgxpool.NewWithConfig(ctx, c.Config)
+	if err != nil {
+		return nil, err
+	}
+	if err = pool.Ping(ctx); err != nil {
+		return nil, err
+	}
+	return &pgxPool{pool}, nil
+}
+
+func NameMatcher(name string) bool {
+	return slices.Contains([]string{"postgres", "pg"}, strings.ToLower(name))
+}
+
+func DecodeConfig(input any) (database.Connector, error) {
+	switch c := input.(type) {
+	case string:
+		config, err := pgxpool.ParseConfig(c)
+		if err != nil {
+			return nil, err
+		}
+		return &Config{Config: config}, nil
+	case map[string]any:
+		connector := new(Config)
+		decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
+			DecodeHook:       mapstructure.StringToTimeDurationHookFunc(),
+			WeaklyTypedInput: true,
+			Result:           connector,
+		})
+		if err != nil {
+			return nil, err
+		}
+		if err = decoder.Decode(c); err != nil {
+			return nil, err
+		}
+		return &Config{
+			Config: &pgxpool.Config{},
+		}, nil
+	}
+	return nil, errors.New("invalid configuration")
+}

backend/v3/storage/database/dialect/postgres/conn.go

@@ -0,0 +1,48 @@
+package postgres
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+type pgxConn struct{ *pgxpool.Conn }
+
+var _ database.Client = (*pgxConn)(nil)
+
+// Release implements [database.Client].
+func (c *pgxConn) Release(_ context.Context) error {
+	c.Conn.Release()
+	return nil
+}
+
+// Begin implements [database.Client].
+func (c *pgxConn) Begin(ctx context.Context, opts *database.TransactionOptions) (database.Transaction, error) {
+	tx, err := c.Conn.BeginTx(ctx, transactionOptionsToPgx(opts))
+	if err != nil {
+		return nil, err
+	}
+	return &pgxTx{tx}, nil
+}
+
+// Query implements sql.Client.
+// Subtle: this method shadows the method (*Conn).Query of pgxConn.Conn.
+func (c *pgxConn) Query(ctx context.Context, sql string, args ...any) (database.Rows, error) {
+	rows, err := c.Conn.Query(ctx, sql, args...)
+	return &Rows{rows}, err
+}
+
+// QueryRow implements sql.Client.
+// Subtle: this method shadows the method (*Conn).QueryRow of pgxConn.Conn.
+func (c *pgxConn) QueryRow(ctx context.Context, sql string, args ...any) database.Row {
+	return c.Conn.QueryRow(ctx, sql, args...)
+}
+
+// Exec implements [database.Pool].
+// Subtle: this method shadows the method (Pool).Exec of pgxPool.Pool.
+func (c *pgxConn) Exec(ctx context.Context, sql string, args ...any) error {
+	_, err := c.Conn.Exec(ctx, sql, args...)
+	return err
+}

backend/v3/storage/database/dialect/postgres/pool.go

@@ -0,0 +1,57 @@
+package postgres
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+type pgxPool struct{ *pgxpool.Pool }
+
+var _ database.Pool = (*pgxPool)(nil)
+
+// Acquire implements [database.Pool].
+func (c *pgxPool) Acquire(ctx context.Context) (database.Client, error) {
+	conn, err := c.Pool.Acquire(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return &pgxConn{conn}, nil
+}
+
+// Query implements [database.Pool].
+// Subtle: this method shadows the method (Pool).Query of pgxPool.Pool.
+func (c *pgxPool) Query(ctx context.Context, sql string, args ...any) (database.Rows, error) {
+	rows, err := c.Pool.Query(ctx, sql, args...)
+	return &Rows{rows}, err
+}
+
+// QueryRow implements [database.Pool].
+// Subtle: this method shadows the method (Pool).QueryRow of pgxPool.Pool.
+func (c *pgxPool) QueryRow(ctx context.Context, sql string, args ...any) database.Row {
+	return c.Pool.QueryRow(ctx, sql, args...)
+}
+
+// Exec implements [database.Pool].
+// Subtle: this method shadows the method (Pool).Exec of pgxPool.Pool.
+func (c *pgxPool) Exec(ctx context.Context, sql string, args ...any) error {
+	_, err := c.Pool.Exec(ctx, sql, args...)
+	return err
+}
+
+// Begin implements [database.Pool].
+func (c *pgxPool) Begin(ctx context.Context, opts *database.TransactionOptions) (database.Transaction, error) {
+	tx, err := c.Pool.BeginTx(ctx, transactionOptionsToPgx(opts))
+	if err != nil {
+		return nil, err
+	}
+	return &pgxTx{tx}, nil
+}
+
+// Close implements [database.Pool].
+func (c *pgxPool) Close(_ context.Context) error {
+	c.Pool.Close()
+	return nil
+}

backend/v3/storage/database/dialect/postgres/rows.go

@@ -0,0 +1,18 @@
+package postgres
+
+import (
+	"github.com/jackc/pgx/v5"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+var _ database.Rows = (*Rows)(nil)
+
+type Rows struct{ pgx.Rows }
+
+// Close implements [database.Rows].
+// Subtle: this method shadows the method (Rows).Close of Rows.Rows.
+func (r *Rows) Close() error {
+	r.Rows.Close()
+	return nil
+}

backend/v3/storage/database/dialect/postgres/tx.go

@@ -0,0 +1,95 @@
+package postgres
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+type pgxTx struct{ pgx.Tx }
+
+var _ database.Transaction = (*pgxTx)(nil)
+
+// Commit implements [database.Transaction].
+func (tx *pgxTx) Commit(ctx context.Context) error {
+	return tx.Tx.Commit(ctx)
+}
+
+// Rollback implements [database.Transaction].
+func (tx *pgxTx) Rollback(ctx context.Context) error {
+	return tx.Tx.Rollback(ctx)
+}
+
+// End implements [database.Transaction].
+func (tx *pgxTx) End(ctx context.Context, err error) error {
+	if err != nil {
+		tx.Rollback(ctx)
+		return err
+	}
+	return tx.Commit(ctx)
+}
+
+// Query implements [database.Transaction].
+// Subtle: this method shadows the method (Tx).Query of pgxTx.Tx.
+func (tx *pgxTx) Query(ctx context.Context, sql string, args ...any) (database.Rows, error) {
+	rows, err := tx.Tx.Query(ctx, sql, args...)
+	return &Rows{rows}, err
+}
+
+// QueryRow implements [database.Transaction].
+// Subtle: this method shadows the method (Tx).QueryRow of pgxTx.Tx.
+func (tx *pgxTx) QueryRow(ctx context.Context, sql string, args ...any) database.Row {
+	return tx.Tx.QueryRow(ctx, sql, args...)
+}
+
+// Exec implements [database.Transaction].
+// Subtle: this method shadows the method (Pool).Exec of pgxPool.Pool.
+func (tx *pgxTx) Exec(ctx context.Context, sql string, args ...any) error {
+	_, err := tx.Tx.Exec(ctx, sql, args...)
+	return err
+}
+
+// Begin implements [database.Transaction].
+// As postgres does not support nested transactions we use savepoints to emulate them.
+func (tx *pgxTx) Begin(ctx context.Context) (database.Transaction, error) {
+	savepoint, err := tx.Tx.Begin(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return &pgxTx{savepoint}, nil
+}
+
+func transactionOptionsToPgx(opts *database.TransactionOptions) pgx.TxOptions {
+	if opts == nil {
+		return pgx.TxOptions{}
+	}
+
+	return pgx.TxOptions{
+		IsoLevel:   isolationToPgx(opts.IsolationLevel),
+		AccessMode: accessModeToPgx(opts.AccessMode),
+	}
+}
+
+func isolationToPgx(isolation database.IsolationLevel) pgx.TxIsoLevel {
+	switch isolation {
+	case database.IsolationLevelSerializable:
+		return pgx.Serializable
+	case database.IsolationLevelReadCommitted:
+		return pgx.ReadCommitted
+	default:
+		return pgx.Serializable
+	}
+}
+
+func accessModeToPgx(accessMode database.AccessMode) pgx.TxAccessMode {
+	switch accessMode {
+	case database.AccessModeReadWrite:
+		return pgx.ReadWrite
+	case database.AccessModeReadOnly:
+		return pgx.ReadOnly
+	default:
+		return pgx.ReadWrite
+	}
+}

backend/v3/storage/database/gen_mock.go

@@ -0,0 +1,3 @@
+package database
+
+//go:generate mockgen -typed -package mock -destination ./mock/database.mock.go github.com/zitadel/zitadel/backend/v3/storage/database Pool,Client,Row,Rows,Transaction

backend/v3/storage/database/repository/clause.go

@@ -0,0 +1,160 @@
+package repository
+
+import (
+	"fmt"
+
+	"github.com/zitadel/zitadel/backend/v3/domain"
+)
+
+type field interface {
+	fmt.Stringer
+}
+
+type fieldDescriptor struct {
+	schema string
+	table  string
+	name   string
+}
+
+func (f fieldDescriptor) String() string {
+	return f.schema + "." + f.table + "." + f.name
+}
+
+type ignoreCaseFieldDescriptor struct {
+	fieldDescriptor
+	fieldNameSuffix string
+}
+
+func (f ignoreCaseFieldDescriptor) String() string {
+	return f.fieldDescriptor.String() + f.fieldNameSuffix
+}
+
+type textFieldDescriptor struct {
+	field
+	isIgnoreCase bool
+}
+
+type clause[Op domain.Operation] struct {
+	field field
+	op    Op
+}
+
+const (
+	schema    = "zitadel"
+	userTable = "users"
+)
+
+var userFields = map[domain.UserField]field{
+	domain.UserFieldInstanceID: fieldDescriptor{
+		schema: schema,
+		table:  userTable,
+		name:   "instance_id",
+	},
+	domain.UserFieldOrgID: fieldDescriptor{
+		schema: schema,
+		table:  userTable,
+		name:   "org_id",
+	},
+	domain.UserFieldID: fieldDescriptor{
+		schema: schema,
+		table:  userTable,
+		name:   "id",
+	},
+	domain.UserFieldUsername: textFieldDescriptor{
+		field: ignoreCaseFieldDescriptor{
+			fieldDescriptor: fieldDescriptor{
+				schema: schema,
+				table:  userTable,
+				name:   "username",
+			},
+			fieldNameSuffix: "_lower",
+		},
+	},
+	domain.UserHumanFieldEmail: textFieldDescriptor{
+		field: ignoreCaseFieldDescriptor{
+			fieldDescriptor: fieldDescriptor{
+				schema: schema,
+				table:  userTable,
+				name:   "email",
+			},
+			fieldNameSuffix: "_lower",
+		},
+	},
+	domain.UserHumanFieldEmailVerified: fieldDescriptor{
+		schema: schema,
+		table:  userTable,
+		name:   "email_is_verified",
+	},
+}
+
+type textClause[V domain.Text] struct {
+	clause[domain.TextOperation]
+	value V
+}
+
+var textOp map[domain.TextOperation]string = map[domain.TextOperation]string{
+	domain.TextOperationEqual:                " = ",
+	domain.TextOperationNotEqual:             " <> ",
+	domain.TextOperationStartsWith:           " LIKE ",
+	domain.TextOperationStartsWithIgnoreCase: " LIKE ",
+}
+
+func (tc textClause[V]) Write(stmt *statement) {
+	placeholder := stmt.appendArg(tc.value)
+	var (
+		left, right string
+	)
+	switch tc.clause.op {
+	case domain.TextOperationEqual:
+		left = tc.clause.field.String()
+		right = placeholder
+	case domain.TextOperationNotEqual:
+		left = tc.clause.field.String()
+		right = placeholder
+	case domain.TextOperationStartsWith:
+		left = tc.clause.field.String()
+		right = placeholder + "%"
+	case domain.TextOperationStartsWithIgnoreCase:
+		left = tc.clause.field.String()
+		if _, ok := tc.clause.field.(ignoreCaseFieldDescriptor); !ok {
+			left = "LOWER(" + left + ")"
+		}
+		right = "LOWER(" + placeholder + "%)"
+	}
+
+	stmt.builder.WriteString(left)
+	stmt.builder.WriteString(textOp[tc.clause.op])
+	stmt.builder.WriteString(right)
+}
+
+type boolClause[V domain.Bool] struct {
+	clause[domain.BoolOperation]
+	value V
+}
+
+func (bc boolClause[V]) Write(stmt *statement) {
+	if !bc.value {
+		stmt.builder.WriteString("NOT ")
+	}
+	stmt.builder.WriteString(bc.clause.field.String())
+}
+
+type numberClause[V domain.Number] struct {
+	clause[domain.NumberOperation]
+	value V
+}
+
+var numberOp map[domain.NumberOperation]string = map[domain.NumberOperation]string{
+	domain.NumberOperationEqual:              " = ",
+	domain.NumberOperationNotEqual:           " <> ",
+	domain.NumberOperationLessThan:           " < ",
+	domain.NumberOperationLessThanOrEqual:    " <= ",
+	domain.NumberOperationGreaterThan:        " > ",
+	domain.NumberOperationGreaterThanOrEqual: " >= ",
+}
+
+func (nc numberClause[V]) Write(stmt *statement) {
+	stmt.builder.WriteString(nc.clause.field.String())
+	stmt.builder.WriteString(numberOp[nc.clause.op])
+	stmt.builder.WriteString(stmt.appendArg(nc.value))
+}

backend/v3/storage/database/repository/crypto.go

@@ -0,0 +1,45 @@
+package repository
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/v3/domain"
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+	"github.com/zitadel/zitadel/internal/crypto"
+)
+
+type cryptoRepo struct {
+	database.QueryExecutor
+}
+
+func Crypto(db database.QueryExecutor) domain.CryptoRepository {
+	return &cryptoRepo{
+		QueryExecutor: db,
+	}
+}
+
+const getEncryptionConfigQuery = "SELECT" +
+	" length" +
+	", expiry" +
+	", should_include_lower_letters" +
+	", should_include_upper_letters" +
+	", should_include_digits" +
+	", should_include_symbols" +
+	" FROM encryption_config"
+
+func (repo *cryptoRepo) GetEncryptionConfig(ctx context.Context) (*crypto.GeneratorConfig, error) {
+	var config crypto.GeneratorConfig
+	row := repo.QueryRow(ctx, getEncryptionConfigQuery)
+	err := row.Scan(
+		&config.Length,
+		&config.Expiry,
+		&config.IncludeLowerLetters,
+		&config.IncludeUpperLetters,
+		&config.IncludeDigits,
+		&config.IncludeSymbols,
+	)
+	if err != nil {
+		return nil, err
+	}
+	return &config, nil
+}

backend/v3/storage/database/repository/doc.go

@@ -0,0 +1,7 @@
+// Repository package provides the database repository for the application.
+// It contains the implementation of the [repository pattern](https://martinfowler.com/eaaCatalog/repository.html) for the database.
+
+// funcs which need to interact with the database should create interfaces which are implemented by the
+// [query] and [exec] structs respectively their factory methods [Query] and [Execute]. The [query] struct is used for read operations, while the [exec] struct is used for write operations.
+
+package repository

backend/v3/storage/database/repository/instance.go

@@ -0,0 +1,54 @@
+package repository
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/v3/domain"
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+type instance struct {
+	database.QueryExecutor
+}
+
+func Instance(client database.QueryExecutor) domain.InstanceRepository {
+	return &instance{QueryExecutor: client}
+}
+
+func (i *instance) ByID(ctx context.Context, id string) (*domain.Instance, error) {
+	var instance domain.Instance
+	err := i.QueryExecutor.QueryRow(ctx, `SELECT id, name, created_at, updated_at, deleted_at FROM instances WHERE id = $1`, id).Scan(
+		&instance.ID,
+		&instance.Name,
+		&instance.CreatedAt,
+		&instance.UpdatedAt,
+		&instance.DeletedAt,
+	)
+	if err != nil {
+		return nil, err
+	}
+	return &instance, nil
+}
+
+const createInstanceStmt = `INSERT INTO instances (id, name) VALUES ($1, $2) RETURNING created_at, updated_at`
+
+// Create implements [domain.InstanceRepository].
+func (i *instance) Create(ctx context.Context, instance *domain.Instance) error {
+	return i.QueryExecutor.QueryRow(ctx, createInstanceStmt,
+		instance.ID,
+		instance.Name,
+	).Scan(
+		&instance.CreatedAt,
+		&instance.UpdatedAt,
+	)
+}
+
+// On implements [domain.InstanceRepository].
+func (i *instance) On(id string) domain.InstanceOperation {
+	return &instanceOperation{
+		QueryExecutor: i.QueryExecutor,
+		id:            id,
+	}
+}
+
+var _ domain.InstanceRepository = (*instance)(nil)

backend/v3/storage/database/repository/instance_operation.go

@@ -0,0 +1,52 @@
+package repository
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/v3/domain"
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+type instanceOperation struct {
+	database.QueryExecutor
+	id string
+}
+
+const addInstanceAdminStmt = `INSERT INTO instance_admins (instance_id, user_id, roles) VALUES ($1, $2, $3)`
+
+// AddAdmin implements [domain.InstanceOperation].
+func (i *instanceOperation) AddAdmin(ctx context.Context, userID string, roles []string) error {
+	return i.QueryExecutor.Exec(ctx, addInstanceAdminStmt, i.id, userID, roles)
+}
+
+// Delete implements [domain.InstanceOperation].
+func (i *instanceOperation) Delete(ctx context.Context) error {
+	return i.QueryExecutor.Exec(ctx, `DELETE FROM instances WHERE id = $1`, i.id)
+}
+
+const removeInstanceAdminStmt = `DELETE FROM instance_admins WHERE instance_id = $1 AND user_id = $2`
+
+// RemoveAdmin implements [domain.InstanceOperation].
+func (i *instanceOperation) RemoveAdmin(ctx context.Context, userID string) error {
+	return i.QueryExecutor.Exec(ctx, removeInstanceAdminStmt, i.id, userID)
+}
+
+const setInstanceAdminRolesStmt = `UPDATE instance_admins SET roles = $1 WHERE instance_id = $2 AND user_id = $3`
+
+// SetAdminRoles implements [domain.InstanceOperation].
+func (i *instanceOperation) SetAdminRoles(ctx context.Context, userID string, roles []string) error {
+	return i.QueryExecutor.Exec(ctx, setInstanceAdminRolesStmt, roles, i.id, userID)
+}
+
+const updateInstanceStmt = `UPDATE instances SET name = $1, updated_at = $2 WHERE id = $3 RETURNING updated_at`
+
+// Update implements [domain.InstanceOperation].
+func (i *instanceOperation) Update(ctx context.Context, instance *domain.Instance) error {
+	return i.QueryExecutor.QueryRow(ctx, updateInstanceStmt,
+		instance.Name,
+		instance.UpdatedAt,
+		i.id,
+	).Scan(&instance.UpdatedAt)
+}
+
+var _ domain.InstanceOperation = (*instanceOperation)(nil)

backend/v3/storage/database/repository/query.go

@@ -0,0 +1,17 @@
+package repository
+
+import (
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+type query struct{ database.Querier }
+
+func Query(querier database.Querier) *query {
+	return &query{Querier: querier}
+}
+
+type executor struct{ database.Executor }
+
+func Execute(exec database.Executor) *executor {
+	return &executor{Executor: exec}
+}

backend/v3/storage/database/repository/statement.go

@@ -0,0 +1,21 @@
+package repository
+
+import "strings"
+
+type statement struct {
+	builder strings.Builder
+	args    []any
+}
+
+func (s *statement) appendArg(arg any) (placeholder string) {
+	s.args = append(s.args, arg)
+	return "$" + string(len(s.args))
+}
+
+func (s *statement) appendArgs(args ...any) (placeholders []string) {
+	placeholders = make([]string, len(args))
+	for i, arg := range args {
+		placeholders[i] = s.appendArg(arg)
+	}
+	return placeholders
+}

backend/v3/storage/database/repository/stmt/column.go

@@ -0,0 +1,43 @@
+package stmt
+
+import "fmt"
+
+type Column[T any] interface {
+	fmt.Stringer
+	statementApplier[T]
+	scanner(t *T) any
+}
+
+type columnDescriptor[T any] struct {
+	name string
+	scan func(*T) any
+}
+
+func (cd columnDescriptor[T]) scanner(t *T) any {
+	return cd.scan(t)
+}
+
+// Apply implements [Column].
+func (f columnDescriptor[T]) Apply(stmt *statement[T]) {
+	stmt.builder.WriteString(stmt.columnPrefix())
+	stmt.builder.WriteString(f.String())
+}
+
+// String implements [Column].
+func (f columnDescriptor[T]) String() string {
+	return f.name
+}
+
+var _ Column[any] = (*columnDescriptor[any])(nil)
+
+type ignoreCaseColumnDescriptor[T any] struct {
+	columnDescriptor[T]
+	fieldNameSuffix string
+}
+
+func (f ignoreCaseColumnDescriptor[T]) ApplyIgnoreCase(stmt *statement[T]) {
+	stmt.builder.WriteString(f.String())
+	stmt.builder.WriteString(f.fieldNameSuffix)
+}
+
+var _ Column[any] = (*ignoreCaseColumnDescriptor[any])(nil)

backend/v3/storage/database/repository/stmt/condition.go

@@ -0,0 +1,97 @@
+package stmt
+
+import "fmt"
+
+type statementApplier[T any] interface {
+	// Apply writes the statement to the builder.
+	Apply(stmt *statement[T])
+}
+
+type Condition[T any] interface {
+	statementApplier[T]
+}
+
+type op interface {
+	TextOperation | NumberOperation | ListOperation
+	fmt.Stringer
+}
+
+type operation[T any, O op] struct {
+	o O
+}
+
+func (o operation[T, O]) String() string {
+	return o.o.String()
+}
+
+func (o operation[T, O]) Apply(stmt *statement[T]) {
+	stmt.builder.WriteString(o.o.String())
+}
+
+type condition[V, T any, OP op] struct {
+	field Column[T]
+	op    OP
+	value V
+}
+
+func (c *condition[V, T, OP]) Apply(stmt *statement[T]) {
+	// placeholder := stmt.appendArg(c.value)
+	stmt.builder.WriteString(stmt.columnPrefix())
+	stmt.builder.WriteString(c.field.String())
+	// stmt.builder.WriteString(c.op)
+	// stmt.builder.WriteString(placeholder)
+}
+
+type and[T any] struct {
+	conditions []Condition[T]
+}
+
+func And[T any](conditions ...Condition[T]) *and[T] {
+	return &and[T]{
+		conditions: conditions,
+	}
+}
+
+// Apply implements [Condition].
+func (a *and[T]) Apply(stmt *statement[T]) {
+	if len(a.conditions) > 1 {
+		stmt.builder.WriteString("(")
+		defer stmt.builder.WriteString(")")
+	}
+
+	for i, condition := range a.conditions {
+		if i > 0 {
+			stmt.builder.WriteString(" AND ")
+		}
+		condition.Apply(stmt)
+	}
+}
+
+var _ Condition[any] = (*and[any])(nil)
+
+type or[T any] struct {
+	conditions []Condition[T]
+}
+
+func Or[T any](conditions ...Condition[T]) *or[T] {
+	return &or[T]{
+		conditions: conditions,
+	}
+}
+
+// Apply implements [Condition].
+func (o *or[T]) Apply(stmt *statement[T]) {
+	if len(o.conditions) > 1 {
+		stmt.builder.WriteString("(")
+		defer stmt.builder.WriteString(")")
+	}
+
+	for i, condition := range o.conditions {
+		if i > 0 {
+			stmt.builder.WriteString(" OR ")
+		}
+		condition.Apply(stmt)
+	}
+}
+
+var _ Condition[any] = (*or[any])(nil)

backend/v3/storage/database/repository/stmt/list.go

@@ -0,0 +1,71 @@
+package stmt
+
+type ListEntry interface {
+	Number | Text | any
+}
+
+type ListCondition[E ListEntry, T any] struct {
+	condition[[]E, T, ListOperation]
+}
+
+func (lc *ListCondition[E, T]) Apply(stmt *statement[T]) {
+	placeholder := stmt.appendArg(lc.value)
+
+	switch lc.op {
+	case ListOperationEqual, ListOperationNotEqual:
+		lc.field.Apply(stmt)
+		operation[T, ListOperation]{lc.op}.Apply(stmt)
+		stmt.builder.WriteString(placeholder)
+	case ListOperationContainsAny, ListOperationContainsAll:
+		lc.field.Apply(stmt)
+		operation[T, ListOperation]{lc.op}.Apply(stmt)
+		stmt.builder.WriteString(placeholder)
+	case ListOperationNotContainsAny, ListOperationNotContainsAll:
+		stmt.builder.WriteString("NOT (")
+		lc.field.Apply(stmt)
+		operation[T, ListOperation]{lc.op}.Apply(stmt)
+		stmt.builder.WriteString(placeholder)
+		stmt.builder.WriteString(")")
+	default:
+		panic("unknown list operation")
+	}
+}
+
+type ListOperation uint8
+
+const (
+	// ListOperationEqual checks if the arrays are equal including the order of the elements
+	ListOperationEqual ListOperation = iota + 1
+	// ListOperationNotEqual checks if the arrays are not equal including the order of the elements
+	ListOperationNotEqual
+
+	// ListOperationContains checks if the array column contains all the values of the specified array
+	ListOperationContainsAll
+	// ListOperationContainsAny checks if the arrays have at least one value in common
+	ListOperationContainsAny
+	// ListOperationContainsAll checks if the array column contains all the values of the specified array
+
+	// ListOperationNotContainsAll checks if the specified array is not contained by the column
+	ListOperationNotContainsAll
+	// ListOperationNotContainsAny checks if the arrays column contains none of the values of the specified array
+	ListOperationNotContainsAny
+)
+
+var listOperations = map[ListOperation]string{
+	// ListOperationEqual checks if the lists are equal
+	ListOperationEqual: " = ",
+	// ListOperationNotEqual checks if the lists are not equal
+	ListOperationNotEqual: " <> ",
+	// ListOperationContainsAny checks if the arrays have at least one value in common
+	ListOperationContainsAny: " && ",
+	// ListOperationContainsAll checks if the array column contains all the values of the specified array
+	ListOperationContainsAll: " @> ",
+	// ListOperationNotContainsAny checks if the arrays column contains none of the values of the specified array
+	ListOperationNotContainsAny: " && ", // Base operator for NOT (A && B)
+	// ListOperationNotContainsAll checks if the array column is not contained by the specified array
+	ListOperationNotContainsAll: " <@ ", // Base operator for NOT (A <@ B)
+}
+
+func (lo ListOperation) String() string {
+	return listOperations[lo]
+}

backend/v3/storage/database/repository/stmt/number.go

@@ -0,0 +1,61 @@
+package stmt
+
+import (
+	"time"
+
+	"golang.org/x/exp/constraints"
+)
+
+type Number interface {
+	constraints.Integer | constraints.Float | constraints.Complex | time.Time | time.Duration
+}
+
+type between[N Number] struct {
+	min, max N
+}
+
+type NumberBetween[V Number, T any] struct {
+	condition[between[V], T, NumberOperation]
+}
+
+func (nb *NumberBetween[V, T]) Apply(stmt *statement[T]) {
+	nb.field.Apply(stmt)
+	stmt.builder.WriteString(" BETWEEN ")
+	stmt.builder.WriteString(stmt.appendArg(nb.value.min))
+	stmt.builder.WriteString(" AND ")
+	stmt.builder.WriteString(stmt.appendArg(nb.value.max))
+}
+
+type NumberCondition[V Number, T any] struct {
+	condition[V, T, NumberOperation]
+}
+
+func (nc *NumberCondition[V, T]) Apply(stmt *statement[T]) {
+	nc.field.Apply(stmt)
+	operation[T, NumberOperation]{nc.op}.Apply(stmt)
+	stmt.builder.WriteString(stmt.appendArg(nc.value))
+}
+
+type NumberOperation uint8
+
+const (
+	NumberOperationEqual NumberOperation = iota + 1
+	NumberOperationNotEqual
+	NumberOperationLessThan
+	NumberOperationLessThanOrEqual
+	NumberOperationGreaterThan
+	NumberOperationGreaterThanOrEqual
+)
+
+var numberOperations = map[NumberOperation]string{
+	NumberOperationEqual:              " = ",
+	NumberOperationNotEqual:           " <> ",
+	NumberOperationLessThan:           " < ",
+	NumberOperationLessThanOrEqual:    " <= ",
+	NumberOperationGreaterThan:        " > ",
+	NumberOperationGreaterThanOrEqual: " >= ",
+}
+
+func (no NumberOperation) String() string {
+	return numberOperations[no]
+}

backend/v3/storage/database/repository/stmt/statement.go

@@ -0,0 +1,104 @@
+package stmt
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+type statement[T any] struct {
+	builder strings.Builder
+	client  database.QueryExecutor
+
+	columns []Column[T]
+
+	schema string
+	table  string
+	alias  string
+
+	condition Condition[T]
+
+	limit  uint32
+	offset uint32
+	// order by fieldname and sort direction false for asc true for desc
+	// orderBy SortingColumns[C]
+	args         []any
+	existingArgs map[any]string
+}
+
+func (s *statement[T]) scanners(t *T) []any {
+	scanners := make([]any, len(s.columns))
+	for i, column := range s.columns {
+		scanners[i] = column.scanner(t)
+	}
+	return scanners
+}
+
+func (s *statement[T]) query() string {
+	s.builder.WriteString(`SELECT `)
+	for i, column := range s.columns {
+		if i > 0 {
+			s.builder.WriteString(", ")
+		}
+		column.Apply(s)
+	}
+	s.builder.WriteString(` FROM `)
+	s.builder.WriteString(s.schema)
+	s.builder.WriteRune('.')
+	s.builder.WriteString(s.table)
+	if s.alias != "" {
+		s.builder.WriteString(" AS ")
+		s.builder.WriteString(s.alias)
+	}
+
+	s.builder.WriteString(` WHERE `)
+
+	s.condition.Apply(s)
+
+	if s.limit > 0 {
+		s.builder.WriteString(` LIMIT `)
+		s.builder.WriteString(s.appendArg(s.limit))
+	}
+	if s.offset > 0 {
+		s.builder.WriteString(` OFFSET `)
+		s.builder.WriteString(s.appendArg(s.offset))
+	}
+
+	return s.builder.String()
+}
+
+// func (s *statement[T]) Where(condition Condition[T]) *statement[T] {
+// 	s.condition = condition
+// 	return s
+// }
+
+// func (s *statement[T]) Limit(limit uint32) *statement[T] {
+// 	s.limit = limit
+// 	return s
+// }
+
+// func (s *statement[T]) Offset(offset uint32) *statement[T] {
+// 	s.offset = offset
+// 	return s
+// }
+
+func (s *statement[T]) columnPrefix() string {
+	if s.alias != "" {
+		return s.alias + "."
+	}
+	return s.schema + "." + s.table + "."
+}
+
+func (s *statement[T]) appendArg(arg any) string {
+	if s.existingArgs == nil {
+		s.existingArgs = make(map[any]string)
+	}
+	if existing, ok := s.existingArgs[arg]; ok {
+		return existing
+	}
+	s.args = append(s.args, arg)
+	placeholder := fmt.Sprintf("$%d", len(s.args))
+	s.existingArgs[arg] = placeholder
+	return placeholder
+}

backend/v3/storage/database/repository/stmt/stmt_test.go

@@ -0,0 +1,18 @@
+package stmt_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/zitadel/zitadel/backend/v3/storage/database/repository/stmt"
+)
+
+func Test_Bla(t *testing.T) {
+	stmt.User(nil).Where(
+		stmt.Or(
+			stmt.UserIDCondition("123"),
+			stmt.UserIDCondition("123"),
+			stmt.UserUsernameCondition(stmt.TextOperationEqualIgnoreCase, "test"),
+		),
+	).Limit(1).Offset(1).Get(context.Background())
+}

backend/v3/storage/database/repository/stmt/text.go

@@ -0,0 +1,72 @@
+package stmt
+
+type Text interface {
+	~string | ~[]byte
+}
+
+type TextCondition[V Text, T any] struct {
+	condition[V, T, TextOperation]
+}
+
+func (tc *TextCondition[V, T]) Apply(stmt *statement[T]) {
+	placeholder := stmt.appendArg(tc.value)
+
+	switch tc.op {
+	case TextOperationEqual, TextOperationNotEqual:
+		tc.field.Apply(stmt)
+		operation[T, TextOperation]{tc.op}.Apply(stmt)
+		stmt.builder.WriteString(placeholder)
+	case TextOperationEqualIgnoreCase:
+		if desc, ok := tc.field.(ignoreCaseColumnDescriptor[T]); ok {
+			desc.ApplyIgnoreCase(stmt)
+		} else {
+			stmt.builder.WriteString("LOWER(")
+			tc.field.Apply(stmt)
+			stmt.builder.WriteString(")")
+		}
+		operation[T, TextOperation]{tc.op}.Apply(stmt)
+		stmt.builder.WriteString("LOWER(")
+		stmt.builder.WriteString(placeholder)
+		stmt.builder.WriteString(")")
+	case TextOperationStartsWith:
+		tc.field.Apply(stmt)
+		operation[T, TextOperation]{tc.op}.Apply(stmt)
+		stmt.builder.WriteString(placeholder)
+		stmt.builder.WriteString("|| '%'")
+	case TextOperationStartsWithIgnoreCase:
+		if desc, ok := tc.field.(ignoreCaseColumnDescriptor[T]); ok {
+			desc.ApplyIgnoreCase(stmt)
+		} else {
+			stmt.builder.WriteString("LOWER(")
+			tc.field.Apply(stmt)
+			stmt.builder.WriteString(")")
+		}
+		operation[T, TextOperation]{tc.op}.Apply(stmt)
+		stmt.builder.WriteString("LOWER(")
+		stmt.builder.WriteString(placeholder)
+		stmt.builder.WriteString(")")
+		stmt.builder.WriteString("|| '%'")
+	}
+}
+
+type TextOperation uint8
+
+const (
+	TextOperationEqual TextOperation = iota + 1
+	TextOperationEqualIgnoreCase
+	TextOperationNotEqual
+	TextOperationStartsWith
+	TextOperationStartsWithIgnoreCase
+)
+
+var textOperations = map[TextOperation]string{
+	TextOperationEqual:                " = ",
+	TextOperationEqualIgnoreCase:      " = ",
+	TextOperationNotEqual:             " <> ",
+	TextOperationStartsWith:           " LIKE ",
+	TextOperationStartsWithIgnoreCase: " LIKE ",
+}
+
+func (to TextOperation) String() string {
+	return textOperations[to]
+}

backend/v3/storage/database/repository/stmt/user.go

@@ -0,0 +1,193 @@
+package stmt
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/backend/v3/domain"
+	"github.com/zitadel/zitadel/backend/v3/storage/database"
+)
+
+type userStatement struct {
+	statement[domain.User]
+}
+
+func User(client database.QueryExecutor) *userStatement {
+	return &userStatement{
+		statement: statement[domain.User]{
+			schema: "zitadel",
+			table:  "users",
+			alias:  "u",
+			client: client,
+			columns: []Column[domain.User]{
+				userColumns[UserInstanceID],
+				userColumns[UserOrgID],
+				userColumns[UserColumnID],
+				userColumns[UserColumnUsername],
+				userColumns[UserCreatedAt],
+				userColumns[UserUpdatedAt],
+				userColumns[UserDeletedAt],
+			},
+		},
+	}
+}
+
+func (s *userStatement) Where(condition Condition[domain.User]) *userStatement {
+	s.condition = condition
+	return s
+}
+
+func (s *userStatement) Limit(limit uint32) *userStatement {
+	s.limit = limit
+	return s
+}
+
+func (s *userStatement) Offset(offset uint32) *userStatement {
+	s.offset = offset
+	return s
+}
+
+func (s *userStatement) Get(ctx context.Context) (*domain.User, error) {
+	var user domain.User
+	err := s.client.QueryRow(ctx, s.query(), s.statement.args...).Scan(s.scanners(&user)...)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &user, nil
+}
+
+func (s *userStatement) List(ctx context.Context) ([]*domain.User, error) {
+	var users []*domain.User
+	rows, err := s.client.Query(ctx, s.query(), s.statement.args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var user domain.User
+		err = rows.Scan(s.scanners(&user)...)
+		if err != nil {
+			return nil, err
+		}
+		users = append(users, &user)
+	}
+
+	return users, nil
+}
+
+func (s *userStatement) SetUsername(ctx context.Context, username string) error {
+	return nil
+}
+
+type UserColumn uint8
+
+var (
+	userColumns map[UserColumn]Column[domain.User] = map[UserColumn]Column[domain.User]{
+		UserInstanceID: columnDescriptor[domain.User]{
+			name: "instance_id",
+			scan: func(u *domain.User) any {
+				return &u.InstanceID
+			},
+		},
+		UserOrgID: columnDescriptor[domain.User]{
+			name: "org_id",
+			scan: func(u *domain.User) any {
+				return &u.OrgID
+			},
+		},
+		UserColumnID: columnDescriptor[domain.User]{
+			name: "id",
+			scan: func(u *domain.User) any {
+				return &u.ID
+			},
+		},
+		UserColumnUsername: ignoreCaseColumnDescriptor[domain.User]{
+			columnDescriptor: columnDescriptor[domain.User]{
+				name: "username",
+				scan: func(u *domain.User) any {
+					return &u.Username
+				},
+			},
+			fieldNameSuffix: "_lower",
+		},
+		UserCreatedAt: columnDescriptor[domain.User]{
+			name: "created_at",
+			scan: func(u *domain.User) any {
+				return &u.CreatedAt
+			},
+		},
+		UserUpdatedAt: columnDescriptor[domain.User]{
+			name: "updated_at",
+			scan: func(u *domain.User) any {
+				return &u.UpdatedAt
+			},
+		},
+		UserDeletedAt: columnDescriptor[domain.User]{
+			name: "deleted_at",
+			scan: func(u *domain.User) any {
+				return &u.DeletedAt
+			},
+		},
+	}
+	humanColumns = map[UserColumn]Column[domain.User]{
+		UserHumanColumnEmail: ignoreCaseColumnDescriptor[domain.User]{
+			columnDescriptor: columnDescriptor[domain.User]{
+				name: "email",
+				scan: func(u *domain.User) any {
+					human, ok := u.Traits.(*domain.Human)
+					if !ok {
+						return nil
+					}
+					if human.Email == nil {
+						human.Email = new(domain.Email)
+					}
+					return &human.Email.Address
+				},
+			},
+			fieldNameSuffix: "_lower",
+		},
+		UserHumanColumnEmailVerified: columnDescriptor[domain.User]{
+			name: "email_is_verified",
+			scan: func(u *domain.User) any {
+				human, ok := u.Traits.(*domain.Human)
+				if !ok {
+					return nil
+				}
+				if human.Email == nil {
+					human.Email = new(domain.Email)
+				}
+				return &human.Email.IsVerified
+			},
+		},
+	}
+	machineColumns = map[UserColumn]Column[domain.User]{
+		UserMachineDescription: columnDescriptor[domain.User]{
+			name: "description",
+			scan: func(u *domain.User) any {
+				machine, ok := u.Traits.(*domain.Machine)
+				if !ok {
+					return nil
+				}
+				if machine == nil {
+					machine = new(domain.Machine)
+				}
+				return &machine.Description
+			},
+		},
+	}
+)
+
+const (
+	UserInstanceID UserColumn = iota + 1
+	UserOrgID
+	UserColumnID
+	UserColumnUsername
+	UserHumanColumnEmail
+	UserHumanColumnEmailVerified
+	UserMachineDescription
+	UserCreatedAt
+	UserUpdatedAt
+	UserDeletedAt
+)

backend/v3/storage/database/repository/stmt/user_condition.go

@@ -0,0 +1,23 @@
+package stmt
+
+import "github.com/zitadel/zitadel/backend/v3/domain"
+
+func UserIDCondition(id string) *TextCondition[string, domain.User] {
+	return &TextCondition[string, domain.User]{
+		condition: condition[string, domain.User, TextOperation]{
+			field: userColumns[UserColumnID],
+			op:    TextOperationEqual,
+			value: id,
+		},
+	}
+}
+
+func UserUsernameCondition(op TextOperation, username string) *TextCondition[string, domain.User] {
+	return &TextCondition[string, domain.User]{
+		condition: condition[string, domain.User, TextOperation]{
+			field: userColumns[UserColumnUsername],
+			op:    op,
+			value: username,
+		},
+	}
+}