pgactive is a PostgreSQL extension designed for active-active database replication, allowing multiple instances within a cluster to accept changes simultaneously. This approach enables various use cases, such as multi-region high availability and reducing write latency, but requires applications to manage complexities like conflicting changes and replication lag. Logical replication, introduced in PostgreSQL 10, is a key component for implementing this topology, while additional features are necessary for full support.

Postgres replication slots utilize two log sequence numbers (LSNs) — confirmed_flush_lsn and restart_lsn — to manage data streaming and retention effectively. The confirmed_flush_lsn indicates the last acknowledged data by the consumer, while the restart_lsn serves as a retention boundary for WAL segments needed for ongoing transactions. Understanding these differences is essential for troubleshooting replication issues and optimizing WAL retention in production environments.