Caching

Purpose

Add a cache with a clear invalidation story, or find out why the existing one is serving stale data. A cache is a second source of truth; introducing one is a consistency decision, not just a performance one.

When to Use

• A read path is slow and the data is read far more often than it is written.
• An upstream dependency is expensive, rate-limited, or unreliable.
• Debugging stale reads, cache stampedes, or unexplained memory growth.

Capabilities

• Cache placement: client, CDN, application, database.
• Strategies: cache-aside, read-through, write-through, write-behind.
• Invalidation: TTL, explicit, event-driven, versioned keys.
• Stampede protection: locking, early recomputation, request coalescing.
• Negative caching and hot-key mitigation.