database-redis

name	database-redis
description	Expert rules for caching, key management, and performance in Redis. Use when implementing Redis caching strategies, managing key namespaces, or optimizing Redis performance. (triggers: **/*.ts, **/*.js, **/redis.config.ts, redis, cache, ttl, eviction)

Redis Best Practices

Priority: P0 (CRITICAL)

• Security:
  • Access Control: Use Redis 6.0+ ACLs (ACL SETUSER) to restrict commands by user/role.
  • Encryption: Always enable TLS for data-in-transit (standard in managed Redis like Azure/AWS).
  • Dangerous Commands: Disable or rename FLUSHALL, KEYS, CONFIG, and SHUTDOWN in production.
• Connection Resilience:
  • Pooling: Use connection pooling with tuned high/low watermarks to avoid connection churn.
  • Timeouts: Set strict read_timeout and connect_retries to handle transient network saturation.

Guidelines

• Key Design:
  • Namespacing: Use colons to namespace keys (e.g., app:user:123, rate:limit:ip:1.1.1.1).
  • Readability vs Size: Keep keys descriptive but compact; avoid keys > 512 bytes.
• Commands & Performance:
  • O(N) Avoidance: Use SCAN instead of KEYS. Use UNLINK instead of DEL for background reclamation of large keys.
  • Lua Scripting: Prioritize EVALSHA for atomic logic; ensure scripts are pre-loaded to save bandwidth.
  • Massive Range: Limit ZRANGE, HGETALL, and LRANGE results with offsets/limits.
• Memory Management:
  • Eviction Strategy: Use allkeys-lru for general caches and volatile-lru for mixed persistent/ephemeral data.
  • Lazy Freeing: Enable lazyfree-lazy-eviction and lazyfree-lazy-expire (Redis 4.0+) to offload cleanup from the main thread.
  • Monitoring: Watch Used Memory RSS vs Used Memory Dataset. Large fragmentation suggests a need for MEMORY PURGE or scaling.

Anti-Patterns

• No sole truth in Redis: Always persist critical data to a durable primary database.
• No large blobs: Split values > 100KB into smaller keys or use Hashes for field access.
• No JSON for objects: Use HSET for object fields to enable O(1) access without full decode.
• No TTL-less keys: Set TTL or eviction policy on all non-permanent keys to prevent unbounded growth.

References

• Best Practices Guide
• Checklist