Software Backend Engineering Use this skill to design, implement, and review production-grade backend services: API boundaries, data layer, auth, caching, observability, error handling, testing, and deployment. Defaults to bias toward: type-safe boundaries (validation at the edge), OpenTelemetry for observability, zero-trust assumptions, idempotency for retries, RFC 9457 errors, Postgres + pooling, structured logs, timeouts, and rate limiting. Scaffolding rule : When scaffolding a new project, show full working implementations for all domain logic — fraud rules, audit logging, webhook handler…