multicache

Multicache is a caching approach that employs multiple caches at different layers or locations to store frequently accessed data. The goal is to improve data retrieval speed, scalability, and fault tolerance by spreading load across several caches and reducing pressure on underlying data stores.

Typical architectures fall into two categories: hierarchical multicache and federated multicache. In hierarchical setups, an application first checks a fast in-process or on-CPU cache; if not found, it queries a next-level cache such as an in-memory distributed cache, finally reaching the backing data store if needed. In federated multicache, data is stored across several independent caches, often using a mapping strategy such as consistent hashing or sharding to route requests; clients may access any cache to reduce hotspots.

Coordination and invalidation are key challenges. Common patterns include cache-aside, write-through, and write-behind strategies, adapted to multiple caches. Cache coherence must be maintained across caches when data is updated; expiration policies and versioning may be used to avoid stale reads.

Use cases include web applications needing high read throughput, content delivery networks, database query results, and microservice architectures where multiple services cache shared data. Benefits include higher hit rates, reduced latency, and improved scalability; drawbacks include increased complexity, potential coherence issues, and additional network overhead.

Related concepts include general caching, distributed caches, and cache coherence in multiprocessor systems. Multicache is a design choice rather than a single standard, with implementations varying by platform and requirements.