How One Engineering Team Debugged and Fixed Five Types of Cache Misses in Production

A software engineering team documented five real-world cache miss scenarios that caused or risked production outages in their system. Issues ranged from cold cache misses and corrupted deserialized data to thundering herd problems, cache penetration by bots querying nonexistent IDs, and a full cache stampede during the holiday season. For each failure mode, the team applied targeted fixes such as versioned cache keys, jittered TTLs with background refresh, negative caching, Bloom filters, and circuit breakers in front of the database. A poorly configured Redis Sentinel setup was identified as a contributing factor in their most severe incident, where every request simultaneously hit the database. The post serves as a practical reference for engineers implementing caching, emphasizing that many cache failures are silent and require deliberate logging and defensive architecture to detect and contain.