Replication
How database replication keeps copies of data on several servers: primaries and replicas, synchronous and asynchronous replication, replication lag and read-your-writes, failover and split brain, multi-primary and leaderless designs, PostgreSQL and MySQL in practice, and what replication does not replace.
CodexBash, , 6 min read
A database on a single server has two weaknesses: if that server fails, the application stops, and if reads grow beyond what it can serve, everything slows down. Replication addresses both by keeping copies of the data on several servers. Almost every production database runs with replicas, whether you manage them yourself or a cloud service does it for you. This article explains how replication works, the trade-offs between its modes, the bugs replication lag causes in applications, and how failover works.
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