Re: Troubleshooting a brief spike in active sessions

On Fri, Jan 9, 2026 at 4:41 PM Dirschel, Steve-CW <
Steve(dot)Dirschel(at)bestbuy(dot)com> wrote:

> Aurora Postgres version 17.4
>
> 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.

Josh B