Understanding MySQL Master‑Slave Replication and Read/Write Splitting

The author describes encountering MySQL performance bottlenecks during load testing and proposes read/write splitting as a remedy.

First, the classic master‑slave replication architecture is introduced: one primary MySQL instance handles writes while multiple replicas continuously synchronize data, providing eventual consistency and improving fault tolerance, scalability, and high availability.

Because replication incurs a delay, reads performed immediately after a write may return stale data; therefore, the decision to read from the primary or a replica depends on the business’s tolerance for real‑time freshness.

After replication, read/write splitting can be applied: all write requests go to the primary, while the bulk of read requests are routed to replicas. The flow is illustrated in a second diagram.

Testing shows that moving most reads to replicas dramatically reduces read latency on the primary, stabilizes response times, and nearly doubles write throughput on the master. A chart of the read/write split effect is also provided.

The article concludes that read/write splitting simplifies scaling, enhances elasticity for services with separate read and write APIs, and serves as an excellent hands‑on learning exercise for developers seeking to master database high‑availability techniques.