Repliciranje kopira podatke iz primarnog databaza na jedan ili više repličnih (standby) servera — za visoku dostupnost (failover ako primarni padne) i čitanje skalabilnosti (raspodjela čitanja). PostgreSQL primarno koristi streaming replication (fizičku) na osnovu write-ahead loga (WAL).
Streaming (fizička) repliciranje
Primary ──(streams WAL: the write-ahead log of changes)──▶ Replica(s)
✓ The primary handles all WRITES
✓ Replicas continuously apply the primary's WAL → stay in sync (near-real-time)
✓ Replicas can serve READ queries ("hot standby") → scale reads
