What are eviction policies in Redis?

Redis has several eviction policies that determine how Redis frees memory when the memory limit (maxmemory) is reached. The main policies are:

• noeviction — when the memory limit is reached, new entries are not added, and an error is returned.
• allkeys-lru — the least recently used (LRU) keys are removed from all keys.
• volatile-lru — the least recently used keys with an expiration time (TTL) are removed.
• allkeys-random — random keys are removed from all keys.
• volatile-random — random keys with TTL are removed.
• volatile-ttl — keys with TTL that expire soonest are removed.

The choice of policy depends on the use case:

• If data preservation is important, noeviction can be used.
• allkeys-lru is often used for caching.
• volatile-* policies are applicable if only temporary keys are important.

In Go, when working with Redis through a client (e.g., go-redis), policies are set on the Redis server side in the configuration, not in the client.