Quotas, Backpressure, and DLQ
Audience: operators tuning Notify delivery limits and engineers redriving the dead-letter queue (DLQ).
This page documents the per-tenant delivery quotas, the backpressure thresholds that protect the engine under load, and the DLQ contract used to recover failed deliveries.
Tracking reference: NR4.
Per-tenant quotas
| Scope | Limit |
|---|---|
| Default (all channels) | 500 deliveries/minute |
| Webhook channels | 200/minute |
| Email channels | 120/minute |
| Chat channels | 240/minute |
- Burst budget: 2× the quota for 60 seconds, then a hard clamp.
Backpressure
Enqueue is rejected when either threshold is exceeded:
- Backlog >
quota × 10, or - DLQ growth > 5%/minute.
Dead-letter queue (DLQ)
- Schema:
../schemas/dlq-notify.schema.json. - Redrive: requires an idempotent
delivery_id/dedupe_keyso replays do not duplicate sends. See Retry and idempotency policy.
Metrics to alert on
- Backlog depth.
- DLQ depth.
- Redrive success rate.
- Enqueue reject count.