If you allocate at most 10 database connections in the pool, and all 10 are used, then any other
thread that needs a connection will be paused for up to blocking-timeout-millis. If a connection becomes available within that time, the thread will be given the connection. If the time expires without a connection becoming available, and exception is thrown. Multiple threads can be waiting for connections, and it is first come, first served, with each having its own timer.
