For T370766 I had to add 11 persons to the integration project. I went through https://horizon.wikimedia.org/project/member/ and added the user per their wikitech username. The additions felt a bit slow and the one I have timed took 43 seconds. Similarly removing a user takes roughly 10 seconds.

I have filed this task merely because 43 seconds sounds a lot too much for adding a user and might indicate there is something broken in the backend.