CacheOnly

CacheOnly is a term used in computing to describe a mode or pattern in which data reads are served exclusively from a local or colocated cache, with access to the primary data store limited or avoided depending on configuration. In strict CacheOnly modes, a read on a cache miss does not trigger a fetch from the backing store and instead returns an absence or error, or follows a predefined fallback path. Many systems offer CacheOnly as a configurable option to support offline operation, low latency, or reduced load on origin services.

How it works

CacheOnly relies on a cache hierarchy or distributed caches to store frequently accessed data. Key mechanisms include cache eviction policies, time-to-live and freshness checks, and invalidation signals to ensure data does not become stale beyond acceptable bounds. In distributed environments, coherence protocols or directory-based approaches coordinate updates so that multiple caches do not diverge on shared data. Writes in a CacheOnly setup may be restricted to the cache, or allowed to propagate to the backing store asynchronously, depending on consistency requirements and the specific implementation.

Use cases and considerations

CacheOnly is commonly used in content delivery networks, edge computing, and read-heavy applications where latency is critical or network access to the primary store is unreliable. It can improve response times and reduce back-end load but introduces risks of stale data and reduced availability if the cache cannot serve a request. Appropriate invalidation, synchronization, and fallback strategies are essential to maintain acceptable consistency and fault tolerance.

See also

Caching, cache coherence, read-through cache, write-through cache, write-back cache, TTL and eviction policies.