Production Cheatsheet

One-screen launch gate. Cite: Going to Production, Connections, Concurrency, Graceful Shutdown, Sandboxed.

Redis config (NOT in your code)

Setting	Value	Why
`maxmemory-policy`	`noeviction`	Eviction silently corrupts queues. Only safe value.
Persistence	AOF, ~1s fsync	Survives restarts without losing pending jobs. Often off by default.

Managed Redis usually ships as a cache (LRU + no persistence). Flip both before launch.

Connection rule

const connection = new IORedis({ maxRetriesPerRequest: null });  // MANDATORY

Class	Held
`Queue`	1 (sharable)
`Worker`	1 + internal duplicate (blocking)
`QueueEvents`	1 + internal duplicate (blocking)

new Queue('email', { prefix: 'myapp-prod', connection });  // isolate envs

Graceful shutdown

let down = false;
async function shutdown() {
  if (down) return; down = true;
  await worker.close();    // no new jobs; waits for active (NO self-timeout!)
  await queue.close();
  await connection.quit();
  process.exit(0);
}
process.on('SIGTERM', shutdown).on('SIGINT', shutdown);

worker.close() never self-times-out. Race it vs your grace period, or accept long jobs stall & get re-queued elsewhere.

Scaling model

Work type	Knob	Note
I/O-bound	`concurrency: N` (high)	Exploits event-loop wait time.
CPU-bound	More worker processes	Scales ~linearly. High concurrency hurts.
Blocks event loop	Sandboxed processor	`useWorkerThreads: true` (v3.13+).

Idempotency — required

Retries, stalls, rate-limit re-queues, flow resumes all re-run jobs. Guard side-effects (idempotency keys, dedup flags, upserts). Non-idempotent = double charges / double sends.

🚀 Launch checklist

☑ Redis: maxmemory-policy noeviction + AOF.
☑ All ioredis: maxRetriesPerRequest: null.
☑ removeOnComplete + removeOnFail on every queue.
☑ SIGTERM/SIGINT → worker.close() + connection.quit().
☑ Idempotent processors.
☑ concurrency for I/O; worker processes for CPU; sandbox if blocking.
☑ Metrics on + stalled → alert.
☑ upsertJobScheduler at boot (idempotent).
☑ Dead-letter queue for terminal failures.
☑ uncaughtException/unhandledRejection handlers (log + exit).
☑ Fail fast if Redis unreachable at startup.