We are installing this SafeExamBrowser https://moodle.org/plugins/quizaccess_seb, for the purpose of testing two thousand remote accesses, you have an idea of the Moodle CPU load using this plugin. We want to apply a remote test, and we have this load issue on the Moodle server.
We have an environment with 200 thousand users with 20 thousand courses.
Thanks a lot.
OK - that isn't going to be as simple as CPU load on your Moodle web app.
You're going to need to look at database connections, database load, distributing and load balancing across multiple servers and finding where the actual bottle neck is, because a single server is not going to cope with that kind of simultaneous quiz access.
I do not want to put a "sales" hat on in the forums, but I know we have recently done this for a couple of clients and I would strongly advise chatting with a Moodle Partner who has that experience and has fully load tested an exam portal at that kind of scale.