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?
3000 users doing what?
3000 concurrent users is a crazy amount. More than enough for me to ask you to justify how you arrived at that figure.
If it involves spending money, getting that wrong would be a very bad thing.
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).