I have a 100k qps workload and we run 10 pgBouncer instances. I ran into the CPU limit with 6. Connections to pgBouncer are persistent so it's not caused by connection churn. The amount of incoming connections is in the low hundreds per instance. I tried without SSL as well and it didn't make a measurable difference.

I'm not quite sure if this is a common problem or if it's our workload. It always made me wonder if moving pooling into Postgres is really a good idea.