If you have 10 application instances each with a pool of 20 connections (half of which are idle), you have 100 active connections and 100 idle connections. If

If you have 10 application instances each with a pool of 20 connections (half of which are idle), you have 100 active connections and 100 idle connections. If you have a single "real" connection pool, the idle pool is effectively shared among all application instances. You can have 100 active connections and 10 (or maybe 20) idle. I have run into this problem, but I solved it with careful tuning of automatic instance scaling parameters, connection pool size and timeout. But this only gets you so far; a single real connection pool would be more effective (at the cost of added complexity).