Thanks in advance!
I have had over 5000 users in a course a number of times and everything was just fine.
Hello Nellie and thank you for your reply. Were those users online at the same time? What is your machine specs?
Moodle scales very well by throwing hardware at the problem. Quizzes are about as bad as it gets for system load.
That's why I asked you the question you didn't answer
If you don't know what you will be doing and what the implications are then I strongly recommend you run a pilot and get some experience (and measurements).