Re: Issues Scaling Postgres Concurrency

On 3/13/23 9:24 AM, Harrison Borges wrote:
> Hello everyone.
>
> I’m running into severe performance problems with Postgres as I increase
> the number of concurrent requests against my backend. I’ve identified
> that the bottleneck is Postgres, and to simplify the test case, I
> created an endpoint that only does a count query on a table with ~500k
> rows. At 5 concurrent users, the response time was 33ms, at 10 users it
> was 60ms, and at 20 users it was 120ms.
>
> As the number of concurrent users increases, the response time for the
> count query also increases significantly, indicating that Postgres may
> not be scaling well to handle the increasing load.
>
> This manifests in essentially a server meltdown on production. As the
> concurrent requests stack up, our server is stuck waiting for more and
> more queries. Eventually requests begin timing out as they start taking
> over 30 seconds to respond.
>
> Am I doing something obviously wrong? Does this sound like normal
> behavior? I'm not very experienced at DB ops so I'm not 100% sure what
> to expect here, but I have worked as a Software Engineer for over 10
> years and I've not encountered problems like this before.

1) https://wiki.postgresql.org/wiki/Slow_Counting

2) Are you using connection pooling?

>
> I would appreciate any insights or advice on how to optimize Postgres
> for high concurrency scenarios. Thank you in advance for your help!

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com