When using the Authorize Project plugin to configure authorization for build execution, this has severe consequences on the overall performances of a Jenkins master because it request information repeatedly "trying to get user details for impersonation" from the Security Realm. This can happen during in a thread that hold the Queue.Lock

An instance will periodically become unavailable or take a very long time in builds especially when the build queue becomes large or when a lot of builds are happening all at the same time.

If start a fresh instance with 2 master executors, configure a "Project default Build Authorization" under Manage Jenkins > configure Global Security, then create a single pipeline and execute it, you will see through FINE logging of hudson.model.User that the {{User#getUserDetailsForImpersonation} is requested 8 times:

Feb 24, 2020 2:42:42 PM FINE hudson.model.User getUserDetailsForImpersonation
Impersonation of the user admin was a success
Feb 24, 2020 2:42:42 PM FINE hudson.model.User getUserDetailsForImpersonation
Impersonation of the user admin was a success
Feb 24, 2020 2:42:42 PM FINE hudson.model.User getUserDetailsForImpersonation
Impersonation of the user admin was a success
Feb 24, 2020 2:42:42 PM FINE hudson.model.User getUserDetailsForImpersonation
Impersonation of the user admin was a success
Feb 24, 2020 2:42:42 PM FINE hudson.model.User getUserDetailsForImpersonation
Impersonation of the user admin was a success
Feb 24, 2020 2:42:42 PM FINE hudson.model.User getUserDetailsForImpersonation
Impersonation of the user admin was a success
Feb 24, 2020 2:42:42 PM FINE hudson.model.User getUserDetailsForImpersonation
Impersonation of the user admin was a success
Feb 24, 2020 2:42:42 PM FINE hudson.model.User getUserDetailsForImpersonation
Impersonation of the user admin was a success

Workaround

Caching can be configured at the Security Realm level depending on the solution (for example for LDAP / Active directory).

Improvement Proposal

I do however think that something could be improved and that since impersonation is happening so frequently, maybe the UserDetailsCache can be used to improve performance.