[Redis runbook]: maxmemory-policy must be volatile-lru when the instance holds locks or session state: under volatile-lru, once volatile keys are exhausted Redis returns OOM on writes instead of evicting locks. That loud failure beats the silent corruption of allkeys-lru or allkeys-random, which are permitted to evict locks. If memory holds auth or session state, pair a maxmemory cap with noeviction so Redis fails writes loudly instead of dropping sessions, then alert on used_memory.

Context: The wrong maxmemory-policy turns a cache miss into silent corruption.

## Matched source
Source: Source: https://github.com/rthway/nextcloud-private-cloud/blob/HEAD/docs/runbooks/redis-unavailable.md
Original query: "Redis eviction policy: volatile-lru protects locks, allkeys-lru can corrupt them"
Key terms: allkeys, corrupt, eviction, locks, policy, protects, redis, them, volatile