Redis
Recommended Redis memory settings for SolidX applications in production.
Mental Model
Redis holds SolidX sessions, not just cache.
- Evicting a session key logs a user out; evicting a cache key only costs a database round trip.
- Redis ships with no memory ceiling, so the default failure mode is the host running out of memory rather than Redis shedding load.
SolidX uses Redis when REDIS_HOST and REDIS_PORT are set, and falls back to an in-process cache otherwise. The in-process fallback is not suitable for more than one instance, since refresh tokens and sessions would not be shared between them.
Recommended Settings
maxmemory 2gb
maxmemory-policy volatile-lruSet maxmemory to roughly 70–80% of the memory available to Redis, leaving headroom for its own overhead and fragmentation. The exact figure matters less than setting one at all.
Why these values
maxmemory — Redis defaults to no limit. Without a ceiling it grows until the host runs out and the process is killed, losing every session at once. With a ceiling, Redis sheds load in a controlled way instead.
volatile-lru — evicts only keys that carry an expiry, discarding the least recently used first. All SolidX session and refresh-token keys carry a TTL, so under pressure the oldest sessions are dropped while cached metadata is left intact.
maxmemory-policy only takes effect once maxmemory is reached. Setting the policy alone changes nothing.
Applying Them
# redis.conf — persists across restarts
maxmemory 2gb
maxmemory-policy volatile-lru
# a running instance — CONFIG REWRITE persists it to redis.conf
redis-cli CONFIG SET maxmemory 2gb
redis-cli CONFIG SET maxmemory-policy volatile-lru
redis-cli CONFIG REWRITE
# docker compose
command: redis-server --maxmemory 2gb --maxmemory-policy volatile-lruOn managed Redis such as ElastiCache or Azure Cache, these are parameter group or portal settings rather than a config file. ElastiCache derives maxmemory from the node size, so only the policy needs choosing.
Verifying
redis-cli info memory | grep -E "used_memory_human|maxmemory_human|maxmemory_policy"A maxmemory_human of 0B means no ceiling is configured.