KNOWLEDGE / Caching / Redis
Cache Invalidation Without Magic
Practical cache-aside patterns, freshness windows, and failure behavior for backend services.
CachingRedisBackend
- DOMAIN
- Backend Engineering
- LEVEL
- Intermediate
- READ
- 7 min
- UPDATED
- Aug 20, 2026
MENTAL MODEL / KEY IDEAS
Keep these in mind
- 01Freshness is a product requirement
- 02Invalidation needs ownership
- 03Protect the source from stampedes
Start with tolerance
Before choosing a cache pattern, define how stale the value may be and what should happen when the source is unavailable.
- TTL
- Stale-while-revalidate
- Hard freshness boundaries
Common patterns
Cache-aside is simple, but writers and readers must agree on invalidation. Versioned keys can make transitions safer.
- Cache aside
- Write through
- Versioned namespaces
Operational behavior
Observe hit rate, fill latency, evictions, and source amplification. A cache that hides those signals becomes a new failure source.