What is database replication?

Answer

Replication keeps copies of a database on multiple servers, typically a primary that accepts writes and one or more replicas that receive the changes. It improves read scalability by spreading queries across replicas, increases availability through failover if the primary fails, and can place data closer to users geographically. Replication can be synchronous, where a write waits for replicas to confirm (stronger consistency, higher latency), or asynchronous, where replicas lag slightly behind (faster writes, possible stale reads). It differs from backups, which protect against data loss but are not live copies serving traffic.