The forum recently moved to AWS, correct? I thought they were meant to be incredibly stable.
I am not sure how much tech babble you want, but ill give you some details about this situation.
AWS as an infrastructure is very stable. However, I had us start at the bottom level as far as server size goes. Didn't want us to have to spend more than we needed to.
We were on the free "micro" tier for servers. now were on the Medium size server. More processor cores, more memory.
We also had what appeared to be a DDOS attack against wordpress/apache. I am not certain though, I went the easy route and updated to the latest LAMP Stack (Lamp is the pre-built server that runs on top of the "hardware" that AWS provides us), and changed all the passwords. Maybe some script kiddie was mad that they missed the deadline to join a buying group...
Unfortunately no server is stable if you use up all the CPU or Memory. Ill be monitoring the processes running in the lamp stack closely, and any exploiters will be ... dealt with... muhahahaha.
Anyways that was it. CPU usage at 100%, Fix = update all software to fix exploits, and upgrade the hardware to increase resources.