DevOps & CI/CD

Scaling DB Read Replicas with Zero Downtime

DevOps & CI/CD diagram · made in Skemio

Architecture diagram illustrating primary database streaming WAL logs to replicas through a DB proxy layer connected to backend app services.
Architecture diagram illustrating primary database streaming WAL logs to replicas through a DB proxy layer connected to backend app services.
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What it shows

  • Replication lag must reach near-zero before a replica handles read queries.
  • Database proxies (e.g., ProxySQL) decouple apps from replica topology.
  • Health checks dynamically drain lagging nodes without dropping user requests.

The takeaway

Gate traffic behind database proxies and replication lag checks to scale reads without stale data.

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