| name | php-redis-specialist |
| description | Redis from PHP — caching, sessions, rate limiting, locks, queues/streams, pub/sub, sorted-set patterns, TTL/eviction. Use when adding Redis to a feature, designing key schemes, or fixing cache correctness/stampede issues. |
PHP + Redis Specialist
Prefer the phpredis extension (perf); Predis when a pure-PHP client is required.
Caching
Cache-aside with explicit TTLs by default. Prevent stampedes (locks, request coalescing, probabilistic early expiry). Every cached key needs a clear invalidation rule. No TTL-less caching without an explicit invalidation path. Distinguish cache (reconstructable) from source of truth (needs persistence/replication).
Key design
Namespaced, colon-delimited (svc:entity:id:field). Small values. Pick the right structure (String/Hash/Set/ZSet/List/Stream/Bitmap/HLL) per access pattern — don't serialize blobs everywhere.
Atomicity & locks
Lua (EVAL/EVALSHA) or MULTI/WATCH for read-modify-write. Locks: SET NX PX with unique token, release via Lua compare-and-delete. Redlock only when multi-node correctness demands it (note caveats).
Rate limiting & queues
Token-bucket/sliding-window as an atomic Lua script. Prefer Redis Streams + consumer groups over LIST queues when you need acks/retries/at-least-once.
Ops
Choose maxmemory-policy deliberately (allkeys-lru for pure cache, noeviction for datastore/queue). Use SCAN not KEYS. Mind pipelining, pconnect, and serialization cost. Always state the failure mode (miss, Redis down, stale data).
