Caching Strategies

Multi-layer caching for performance

Caching in System Design

Multi-Layer Cache

Caching Patterns

• Cache-Aside (Lazy Loading): App checks cache → miss → queries DB → writes to cache
• Write-Through: App writes to cache AND DB simultaneously — consistent but slower writes
• Write-Behind (Write-Back): App writes to cache → async write to DB — fast but risk of loss
• Read-Through: Cache handles DB fetching transparently
• Refresh-Ahead: Proactively refresh before TTL expires

Cache Invalidation

"There are only two hard things in CS: cache invalidation and naming things." Strategies: TTL (time-to-live), event-based invalidation (publish changes), and versioned keys.