- temporary storage - used to store frequently accessed data in memory or results of expensive computations - used to speed up servicing requests - much faster than [[Databases]] - can reduce their workload - but stored in volatile [[Memory]] - cache practices - use a cache when data is read frequently but infrequently modified - implement an expiration date to clear the data - use multiple cache servers across multiple data centers for redundancy - when cache is full, requests to add items to cache will cause certain items to be removed (called cache eviction) - common policy is to remove via LRU (least recently used)