synchronous-replication · shipping

Synchronous replication

Synchronous replication makes successful completion depend on acknowledgement that a specified set of replicas has reached the processing stage required by the replication contract.

Name the acknowledgement boundary instead of assuming that synchronous means query-visible. PostgreSQL 18 distinguishes a standby filesystem write, durable WAL flush and transaction replay; configured synchronous standbys are required for remote waiting. This database usage is broader than a storage contract requiring completed remote disk writes. Required replicas add latency and their unavailability can block commits.

Relations

related

asynchronous-replication, replication-lag, mirroring, io-fencing, chain-replication, log-sequence-number

Citations

1. PostgreSQL 18: WAL settings, synchronous_commit (accessed 2026-10-12)
2. PostgreSQL 18: synchronous_standby_names (accessed 2026-10-12)
3. PostgreSQL 18: warm standby and synchronous replication (accessed 2026-10-12)
4. Replication acknowledgements: received, durable, applied (accessed 2026-10-12)

JSON: /data/terms/synchronous-replication.json