We have a large moodle system in our organisation with about 34000 users consuming the e-learning content in the form of scorm courses. The moodle system is setup on a 32Core 128GB RAM Windows 2012 R2 VM with Moodle 3.4 version running on mysql 5.7.
Towards the end of the course evaluation we had a spurt in traffic to our moodle site with almost 50% (17K) of the users trying to access the quiz modules.
Though application ran without any visible decrease in speed, users got frequent DB connection failed popup messages and experienced DB errors during quiz also. Mysql was tuned using mysqltuner script. Still the error persisted. It seems like mysql is refusing further connections after a limit, though the total connections to mysql were less than max_connections limit.
Our organisation requires at least 16K people to be able to access the quiz concurrently. Can someone guide how to make this feasible.