[film42]

The real problem is working with postgres’ “each connection is a process” model. Pgbouncer puts an evented pool in front of postgres to deal with this. Apps that are aggressive with DB will not benefit from having an evented pool in front. However, web apps (think rails) will have connections checked out even if they don’t need them. Pgbouncer helps here. If your app recycles DB connections when not in use, that leads to connection thrashing and higher latency, which pgbouncer can help with. But you’re right that at some point, the DB is the bottleneck. For most people, it’s the number of connections, because postgres makes a process for each connection.