Backend Engineering Edho Ferdian

---
name: backend-engineering-edho-ferdian
description: >-
  Authoring server-side code between the API contract and the datastore —
  layering and ports/adapters boundaries, error taxonomy and resilience
  (typed errors, Result style, retry with backoff, circuit breakers),
  background jobs and queues, structured logging emission, and adding a new
  integration that matches the repo's existing connector pattern. The
  backend counterpart to frontend-engineering-edho-ferdian. Framework
  guides: NestJS and Ruby on Rails (service/form/query objects, Hotwire,
  Rails 8 Solid stack). Trigger phrases: "struktur service layer", "error
  handling di backend", "retry/circuit breaker", "background job / queue",
  "tambah integrasi baru", "bikin app Rails", "Rails service object".
---

# Backend Engineering — Edho Ferdian Mode

## Where this sits

- `api-design-edho-ferdian` decides the **contract** at the boundary.
- `data-layer-patterns-edho-ferdian` decides the **storage** behind it.
- This skill is the **middle**: how the code between them is layered, how it
  fails, and how it defers work.
- `code-review-edho-ferdian` reviews the result — in particular
  `silent-failure-lens.md`, which is the review-side mirror of
  `references/error-and-resilience.md` here. Cross-reference, never restate.

## References

- `references/error-and-resilience.md`
- `references/llm-pipelines.md` — regex-first parsing with confidence-scoring
  as the LLM gate, plus cost-aware model routing, budget tracking, retry
  policy, and prompt caching for pipelines that call an LLM API.
- `references/scheduled-collection.md` — unattended collect/enrich/store
  pipelines (scrapers, feed pollers, report builders): source selection,
  per-source failure isolation, LLM-enrichment batching and fallback,
  prompt-injection rules for untrusted scraped content, idempotent upsert,
  and cron/alerting operations. Covers the background-job concerns
  (idempotency, dead-letter-style backfill, run scheduling) for this class of
  job — see the note below for what it does not cover.
- `references/nestjs.md` — NestJS project structure (`common/`, `config/`,
  `modules/<fitur>/` with module-local DTOs), canonical bootstrap (global
  `ValidationPipe`, `ClassSerializerInterceptor`, `HttpExceptionFilter`), env
  validation at boot, repository/transaction placement, and background
  jobs/event consumers in their own modules. Not speculative — this is the
  framework behind `ghostfolio`, a real project in Edho's stack.
- `references/rails.md` — Rails 7.1+/8.x authoring: directory contract,
  when to extract a service/form/query object or ViewComponent, service
  result objects and transactions, ActiveRecord discipline (eager loading,
  callbacks, no `default_scope`), idempotent jobs, Hotwire, and the Rails 8
  Solid stack. Review and build-failure lenses for Ruby live in
  `language-code-review-edho-ferdian` and `build-fix-edho-ferdian`.

- `references/layering-and-boundaries.md` — ports & adapters (hexagonal
  architecture) with a framework-agnostic dependency-direction diagram, the
  repository-vs-service layer split with a misplaced-concern test, the
  composition root (NestJS DI and hand-wired bootstrap variants), a six-step
  migration playbook for entangled/legacy code, and a checklist for adding a
  new integration cleanly through the same port/adapter seam.
- `references/jobs-and-queues.md` — generic queue-backend reference, distinct
  from `references/scheduled-collection.md` (which covers the
  scheduled-collection job shape specifically): backend choice (BullMQ vs
  SQS vs Postgres-based pg-boss/graphile-worker), worker-pool concurrency
  sizing, retry/backoff classification, dead-letter queues generically, job
  idempotency keys, and queue observability.

## External docs (fixed — see skill-authoring-edho-ferdian's canonical contract)

Before using a fast-moving or rarely-touched framework/queue/ORM API surface
(new integration, version upgrade, NestJS/BullMQ/pg-boss specifics), resolve
it live via Context7 rather than from memory. Full contract:
`skill-authoring-edho-ferdian` §9.

## Surgical changes (fixed — see skill-authoring-edho-ferdian's canonical contract)

This skill inherits the default as-is: when extending or fixing an existing
service, error path, or job, change only what the task requires — don't
relayer or restructure adjacent, already-working code as a side effect. Full
contract: `skill-authoring-edho-ferdian` §10.

## Language routing (fixed — see skill-authoring-edho-ferdian's canonical contract)

Communication to the user in Bahasa Indonesia; code, comments, and any
generated files in English — fixed, never ask. Full contract:
`skill-authoring-edho-ferdian` §7.