API integrations that do not break at 3am

Every integration eventually fails partway through. The provider times out after committing, your process restarts mid-batch, or a webhook is redelivered a day later. Design for that on day one.

Idempotency keys make retries safe. Generate one per logical operation, store it, and short-circuit if you have already processed it. This costs one table and saves entire weekends.

Give retries a budget. Exponential backoff with a cap, then move the job to a dead-letter queue with the full request and error attached. Silent infinite retries are worse than a visible failure.

Verify webhook signatures with a constant-time comparison before parsing the body. An unverified public endpoint that writes to your database is not an integration, it is an invitation.