Recaching

Recaching is the practice of reloading or refreshing data into a cache after it has been evicted, expired, or otherwise made unavailable. It is used to preserve high cache hit rates and reduce latency by ensuring frequently accessed data remains readily available. Recaching can be reactive, occurring in response to a cache miss when the data is requested again, or proactive, where the system periodically refreshes cached items before their TTL expires or after changes are detected.

Methods vary across systems. Lazy recaching occurs on-demand when data is requested again after eviction. Proactive or warming recaching runs background tasks to prefetch data based on access patterns, popularity, or anticipated changes. Techniques include time-based refresh, event-based invalidation and refresh, and continuous background refresh pipelines that fetch updated versions from the primary data store and replace stale entries in the cache.

Benefits of recaching include reduced load on the primary data store, lower latency for end users, and smoother traffic handling during high demand or content updates. Trade-offs involve added load on the origin during refresh, the risk of serving stale data if refresh intervals are too long, and increased complexity in maintaining coherence across multi-tier caches.

Applications span web content delivery networks, application-level caches, database query caches, and distributed in-memory stores. Recaching complements eviction and invalidation policies and is often part of a broader cache management strategy that includes TTLs, eviction policies, and coherence guarantees.