Database Replication

Replication is the process of copying data from one database (the primary/master) to one or more other databases (replicas/standbys) automatically and continuously, for read scaling, failover, or geographic distribution.

In the common primary-replica pattern, writes go to the primary and are streamed to replicas (often via the write-ahead log), which typically serve read-only queries — spreading read load across multiple servers. Replication also underpins high availability: if the primary fails, a replica can be promoted to take over with minimal data loss, depending on whether replication was synchronous or asynchronous.

Replication is not the same as backup: a corrupted or accidentally deleted row replicates to every replica just as reliably as a good one does.