Read Replica

A read replica is a copy of a database that receives a stream of changes from the primary and serves read-only queries. It scales read-heavy workloads horizontally and isolates expensive analytics from the write path.

Worked example: point reporting dashboards and search at replicas while all writes go to the primary, and add more replicas as read traffic grows. Gotcha: replication is asynchronous, so a replica can lag the primary by milliseconds to seconds — a user who writes then immediately reads from a replica may not see their own change (the “read-your-writes” problem), which is why some reads must go to the primary.