Systems and methods for preemptive adjustments of connections in a database connection pool are provided. In example embodiments, a number of quality of service engines analyze database connection pool metrics data to generate instructions to increase or decrease the number of connections in a connection pool, preemptively, before shortages or surpluses of connections occur. Corrective engines can analyze performance of the quality of service engines and can, when necessary, instruct the quality of service engines to modify their prediction mechanisms.