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Eviction vs TTL — Two Different Mechanisms#

Eviction and TTL are two separate mechanisms that both delete keys from a cache. They're easy to confuse but operate on completely different triggers, and both can apply to the same key.

Eviction and TTL are two separate mechanisms

TTL — time-based. Key deleted when its timer runs out, regardless of memory pressure. Eviction — memory-based. Triggered only when cache is full and needs space for a new key. Both can apply to the same key. Whichever fires first wins.