DataDirect is not free but I guess we are discussing technical merits here. For them pooling happens in the connectivity layer and exposes proper pool controls such as minimum and maximum pool size, connection lifetime behavior, and optional connection state reset.

More importantly, it has capabilities that PgBouncer is not designed to provide. It can maintain alternate PostgreSQL servers, retry connections, randomize connection attempts across primary/alternate servers, and has explicit failover modes. The application retains a real PostgreSQL session while the driver handles connection reuse and failure handling.

That matters because of PgBouncer big technical compromise that is transaction pooling. This breaks the assumption that one client connection is the PostgreSQL backend session.

Consequently, several session scoped PostgreSQL features do not work normally in transaction pooling. PgBouncer own compatibility table, lists some of the limitations: https://www.pgbouncer.org/features.html

DataDirect does not need to solve that particular problem because its architecture does not perform that same transaction level back end swapping.