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LRU eviction.

also: LRU · least recently used · eviction policy · eviction policies

Evicting the entry that hasn't been used for the longest time when the cache is full; the usual default policy.

the two-minute refresher

Eviction answers: the cache is full, what do we drop?
LRU drops the least recently used; LFU the least frequently used; FIFO the oldest.
LRU is a good general policy, but a one-time scan can flush hot data.
Redis defaults to noeviction; set allkeys-lru (or similar) for a cache.

Where the course teaches it

W00 · Part 6System Design Terminology & Theorylearn it →

Related concepts

Cache hit ratio
Cache-aside