pglogical
PostgreSQL extension for logical replication. 2ndQuadrant (now EDB) 2015. Forerunner of built-in logical replication (since PG 10, 2017). Many features still only in the extension: bidirectional replication, filtering, conflict resolution.
Use today: zero-downtime PG version upgrades (sync data to new version, swap traffic), cross-region replication, selective sync. Distinct from streaming replication: pglogical replicates logical changes (INSERT/UPDATE), not physical WAL bytes → can replicate between different PG versions + architectures. BDR (Bi-Directional Replication, also EDB) builds on top for multi-master. Built-in logical replication since PG 10 is enough for simple use cases — pglogical for advanced.