A production API route is a boundary, not a collection of queries. Authenticate first, validate a bounded payload, authorize the specific operation, and only then enter the database workflow.
Use transactions when multiple writes represent one business event. Add idempotency to operations clients may safely retry, especially payments, job execution, and external webhooks.
Return stable error shapes and log structured operational context without leaking credentials or personal data. The result is an API that is easier to integrate, debug, and evolve.