Moodle Quiz Activity with 500 Concurrent User

We have experienced a Quiz Activity with 500 concurrent user and i want share this experience with you. Because these insights are really valuable for system administrators, that i could not find any suggestion before this Quiz Activity.  Let me write the details about the system and the quiz activity.
We have installed moodle on a virtual machine VMWare with the following configuration.

We set the vm cpu to 16 shared vcpu,  and 24GB shared RAM
Running Centos 7.0 Minimal with php5.X, apache and mariadb with 700 max_connection setting.
Quiz activity with 20 Question and 30 Minute timespan and 17 Minute attempt time limit. 2 Question per page. Question order and choices were shuffled. Auto submit open attempt setting was on.

CPU and RAM usage was crucial for us. We see maximum 12 GB ram usage which is roughly 1 GB per 50 User
We see %95 CPU usage when the quiz started.

Before quiz started i stopped cron jobs and automated course backups.