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.klaver@aklaver.com