Craig James <cjames(at)emolecules(dot)com> writes: > ... This would result in a thousand > or so Postgres connections on a machine with 32 CPUs.
> So the question is: do idle connections impact performance?
Yes. Those connections have to be examined when gathering snapshot information, since you don't know that they're idle until you look. So the cost of taking a snapshot is proportional to the total number of connections, even when most are idle. This sort of situation is known to aggravate contention for the ProcArrayLock, which is a performance bottleneck if you've got lots of CPUs.
You'd be a lot better off with a pooler.
(There has been, and continues to be, interest in getting rid of this bottleneck ... but it's a problem in all existing Postgres versions.)