Recently, there was an incident where our server was attacked by a large number of requests. Unfortunately, the server was hosting a forum service. Assuming that the attack point was the forum homepage, each request would query the database and there were a lot of joins. Some of the instructions were POST, which would update the database. This caused the database to lock up and the CPU to skyrocket, leading to a crash.
If the forum was self-written, we could add a cache like Redis between the database and application. However, this forum system is someone else’s and we cannot modify it.