Reliable integrations: idempotency, retries, DLQ

Integrations don’t fail as a single bug—they fail as a chain: timeout → retry → duplicate order → manual cleanup. Production integrations need error discipline.

Reliability patterns

• Idempotency: reprocessing the same event doesn’t create duplicates.
• Retries: only retry safe operations; use exponential backoff.
• DLQ: broken messages don’t block the queue.
• Tracing: correlation IDs across logs and events.
• Alerts: spikes in 4xx/5xx, latency, queue depth.

What “idempotent” means in practice

Store a unique key per operation (e.g., order_id + event_type) and make your handler “return success” if the operation was already applied. This turns webhook retries into a non‑issue.

Retry policy (simple and effective)

• Retry network/timeouts and 5xx.
• Don’t blindly retry 4xx—fix the payload or credentials.
• Cap attempts and send to DLQ with context for manual review.

Log payloads (sanitized), validation result, outgoing request, response code, duration, and idempotency key.