Of course, non-blocking code runs better 🙂 For DB connection pool we want to make a suspendable queue, so that it blocks less. While it waits for connection it is normally suspended (doesn’t use a thread), but when connection is available the thread is blocked on any JDBC operation. Fully async drivers are available as open source libs for MySQL and Postgress, just search for it. I think vert.x recently introduced something about it.