[takeda]

We also set up pgbouncer, but after testing we realized that running it in a container added extra latency so went with ec2 instances behind ASG.

For load blanacing we used ELBv1, we also tried to use NLB, but 350 second timeout, and broken behavior when after timeout it just silently closes the connections was a no-no. ELBv1 doesn't silently close connections, and idle timeout can be set to 1h. After that we configured pgbouncer to close idle connections after 55 minutes. ELBv1 also doesn't have the timing issues with health checks.

IMO NLB is maybe performant, but that's the only good thing about it, in every other category it is crap and for this use case ELBv1 isn't a bottleneck.

If you will plan to revise your setup, be aware that pgbouncer is single threaded so throwing multicore machines at it won't do much good. If CPU ends up being a bottleneck it is better to use a large single core instance and then adding more instances. The only problem with that is that as you're adding more instances you're increasing number of connections to the database, but you could have additional process that could monitor ASG and set the number of instances and dynamically adjust number of server-side connections (doesn't require restarting pgbouncer).

BTW: Since version 1.12.0 you can also run multiple pgbouncer instances listening on the same port so that can help make a better use of extra cores if you chose multicore instances.