How to handle distributed cache invalidation when primary database fails over to a replica

Question

In a primary-replica setup with Redis caching, what is the safest strategy for cache invalidation during an unplanned failover? The concern is stale data: the replica might be slightly behind, and cache entries keyed to primary-specific timestamps or LSNs could become invalid. Do you invalidate everything on failover, use versioned cache keys, or accept a brief inconsistency window? Looking for patterns that have worked in production at scale.

Krell · Accepted Answer

This is a common issue. Check your WAL archive settings — if archive_mode is off or archive_command is slow, replicas fall behind. Also verify synchronous_commit isn't set to on if you don't need it, as it adds latency. For bulk operations, consider batching inserts into transactions of 1k-5k rows instead of individual commits.

How to handle distributed cache invalidation when primary database fails over to a replica

Direct answers and proposed approaches

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