Asynchronous replication
Also called: async replication
Asynchronous replication means the primary commits and returns to the client without waiting for any standby to confirm it received the WAL. The standby catches up a moment later. It's the default and the only practical choice across long (cross-region) network distances.
What this means
The primary commits and answers the client without waiting for any standby to confirm it got the change; the standby catches up a moment later. It's the default, and over long distances it's really the only practical choice, but it does mean a sudden loss of the primary can lose the last unsent changes.
Why it matters operationally
It keeps commit latency low by not paying a network round-trip per transaction, but it means a small, bounded window of recent commits can be lost if the primary dies before the standby receives them. That window is your RPO.