cachexi

Cachexi is a theoretical framework for data caching designed to optimize performance in heterogeneous storage environments. It describes a multi-layer caching system that coordinates in-memory, on-disk, and remote caches to reduce data access latency and bandwidth usage. The term is used in academic and industry discussions to illustrate advanced caching concepts, rather than as a single implementation.

Design goals include data locality, predictable latency, and scalability. Cachexi systems model data items as cacheable objects with metadata such as size, access frequency, and freshness. They employ a global coordination layer that assigns objects to cache layers based on predictive models and live metrics.

Core components include cache agents mounted on compute nodes, a central directory or distributed hash table to map keys to caches, and an eviction policy that combines recency, frequency, and size constraints. Cachexi emphasizes adaptive prefetching, where future item requests are probabilistically loaded into closer caches.

Operations and consistency: Cachexi aims for eventual consistency or strong consistency depending on configuration. It uses invalidation messages and versioning to maintain coherence. Failure handling includes replication, checkpointing, and graceful degradation when caches fail.

Limitations and criticism: as a theoretical construct, Cachexi faces challenges including coordination overhead, bursty traffic from prefetching, and complexity of tuning across diverse workloads. In practice, implementations resemble existing distributed caching systems, such as memcached or Redis, with more elaborate tiering.

Related topics include caching, memory hierarchy, distributed cache, prefetching, and eviction policy.