# Which Problems Are Solved
Improve performance by removing a GetUserByID call. The call also
executed a Trigger on projections, which significantly impacted
concurrent requests.
# How the Problems Are Solved
Token creation needs information from the user, such as the resource
owner and access token type.
For client credentials this is solved in a single search. By getting the
user by username (`client_id`), the user details and secret were
obtained in a single query. After that verification and token creation
can proceed. For JWT profile it is a bit more complex. We didn't know
anything about the user until after JWT verification.
The verification did a query for the AuthN key and after that we did a
GetUserByID to get remaining details.
This change uses a joined query when the OIDC library calls the
`GetKeyByIDAndClientID` method on the token storage. The found user
details are set to the verifieer object and returned after verification
is completed.
It is safe because the `jwtProfileKeyStorage` is a single-use object as
a wrapper around `query.Queries`.
This way getting the public key and user details are obtained in a
single query.
# Additional Changes
- Correctly set the `client_id` field with machine's username.
# Additional Context
- Related to: https://github.com/zitadel/zitadel/issues/8352
