# Quotas, backpressure, and DLQ (NR4)

- Per-tenant quotas: 500 deliveries/minute default; channel overrides: webhook 200/min, email 120/min, chat 240/min.
- Burst budget: 2x quota for 60 seconds, then hard clamp.
- Backpressure: reject enqueue when backlog > quota*10 or DLQ growth > 5%/min.
- DLQ schema: `docs/notifications/schemas/dlq-notify.schema.json`; redrive requires idempotent `delivery_id`/`dedupe_key`.
- Metrics to alert: backlog depth, DLQ depth, redrive success rate, enqueue reject count.