This application mainly runs 3 queries very frequently- around 12000 executions per second across the 3. Normally the server handles this fine and at any given time there are between 0 - 10 active sessions running the queries. The 3 queries are tuned- doing 3-7 logical reads per execute and run in < .1 millisecond.
Periodically there will be a huge spike in active sessions up to 400+ sessions all on CPU (it can be higher depending on how many app servers are in the mix at the time). This spike will last 2-5 seconds but it causes an increase in app response time which is a problem.
I'm not super familiar with Aurora, but I've seen this caused by a few different things in vanilla Postgres. I don't think Aurora has checkpoints, so it's probably not that. I have seen where a vacuum can cause various Postgres buffers to have a lot of churn, which can cause higher query latency for a period of time. I have also seen temporary increased disk latency to cause higher query latency.
