Troubleshoot Redis

When to use this skill

• The Fork/COW Storm: Persistence fork causes memory to double via copy-on-write. OOM kill or massive latency spike.
• The Event Loop Wedge: A single slow command (KEYS *, large SORT, Lua script) blocks all other clients.
• The Replication Backlog Overflow: Replica falls behind, backlog wraps, full resync triggered; which triggers another fork.
• The Memory Pressure Spiral: Eviction starts, evicted keys are re-requested, cache miss triggers re-population write which evicts more keys.
• The Connection Exhaustion Cascade: maxclients hit, new connections rejected, applications retry aggressively, making it worse.
• Any time the user reports a Redis service behaving outside its expected envelope (elevated errors, latency, saturation, resource exhaustion, or unexpected restarts).
• An on-call engineer is paging on a Netdata alert tied to a Redis instance and wants a structured triage path.