backend-implementation

name	backend-implementation
description	Implement business logic cleanly: keep the framework at the edges with logic in testable use-cases, model errors explicitly (expected vs bug), validate inputs into domain types at the boundary, add idempotency keys for retried operations, and use the outbox for write-then-publish.

Backend Implementation

Framework at the edges

Logic in plain testable use-cases; HTTP/ORM/framework in thin adapters. A controller full of rules is untestable.

Errors

Distinguish expected failures (validation/not-found/conflict) from bugs; typed results mapped to status at the edge. No bare catch-all.

Validate at the boundary

Parse-and-validate inputs into domain types; the core works with valid data.

Idempotency + outbox

Dedup key for retried work (webhooks/payments/async). Outbox: write the event in the same transaction as the state change so you never publish for a rolled-back write.