Backend Patterns Skill

Degree of freedom: MIXED. Which pattern to apply [HIGH freedom]; existing-architecture probes and the validation list [LOW freedom — run exactly].

How to reason

1. Observe — existing server/api/actions, ORM, queues, cache
2. Interpret — missing pattern vs duplicate vs wrong layer
3. Classify — reuse / add-queue / add-cache / add-rate-limit / edge-fn
4. Severity — unauthenticated mutation outranks a missing cache

Worked example

Observe: createOrder sends email inline; no Inngest/queue; checkout p95 4s. Interpret: confirmation is post-response work, not request-path. Classify: after() or an order/created job; keep the write transactional. Verify: order row commits; email/inventory run after response; retries do not double-charge.