Node and TypeScript Backend Engineering
Make accepted work bounded, observable, and owned through completion or failure. Preserve the application's framework and module choices unless changing them solves the requested problem.
Working Loop
For a small fix, inspect the affected path and use the relevant reference. For broader implementation or review, trace:
- Runtime and module boundary. Identify the deployed Node version, package manager, actual start command, module format, emitted artifact, and dependency initialization owner.
- One terminal outcome. Trace input through the handler or task to its result, error, timeout, or cancellation. Separate caller completion from the actual domain effect; an abandoned response does not prove a write failed.
- Admission and cancellation. Locate the constrained resource and its queue owner. Bound waiting and running work, include queue time in deadlines, propagate cancellation, and assign cleanup and late-result handling.
- Stream or worker handoff. Preserve backpressure, framing, data ownership, task identity, and terminal cleanup. Ordinary
async code does not offload CPU work.
- Validation and serialization. Verify the actual parser, validator, handler input, response serializer, and framework scope. Type inference is a separate assurance.
- Drain and evidence. Stop admission, settle or reconcile accepted work within a deadline, release resources, and verify the affected failure path as well as success.
Do not expand a routine endpoint change into a new architecture, pool, framework, or test harness without a demonstrated need.
Reference Routing
Read only the material needed:
- Runtime, modules, and async contracts: loader failures, event-loop stalls, async races, readiness, terminal ownership, messaging adapters, and graceful drain.
- Streams, backpressure, and cancellation: large inputs, framing, slow consumers, stream topology, and partial completion.
- Workers and bounded capacity: CPU offload, task queues, clone/transfer/share semantics, correlation context, and worker failure.
- Fastify and Express HTTP lifecycle: hook and middleware placement, terminal response ownership, schemas, type providers, serialization, and transport boundaries.
- Testing and packaging:
node:test, fixture ownership, mock isolation, actual package loading, and focused verification.
- Reference index and source scope: provenance and version-sensitive refresh guidance.
Ownership and Handoffs
This skill implements Node runtime adapters, request/task lifecycle, transaction use, and actual domain effects.
| Unresolved decision |
Primary owner and handoff |
| Observable HTTP/OAS/media/error or consumer compatibility |
api-contract-engineering; pass operation identity, versions, expected contract, and actual request/response evidence. Implement the agreed adapter behavior here. |
| Distributed authority, delivery, durable idempotency, queue/log guarantees |
system-design; pass effect boundary, task/message identity, timeout uncertainty, and failure window. |
| Event-time processing, pipeline publication, replay/backfill |
data-engineering; pass source position, output/effect boundary, and observed completion state. |
| Engine constraints, isolation, locks, plans, or restore proof |
database-engineering; retain connection/session and transaction cleanup here. |
| Browser state, React/Next rendering, server-client UI boundary |
web-frontend-engineering. |
| General verification strategy or change lifecycle |
qa-testing or software-engineering; retain Node runner, fixture, and package mechanics here. |
| Threat model and control design, or independent security verdict |
application-security-engineering or security-review; implement the selected runtime controls here. |
| Deployment substrate or operated reliability |
platform-devops-engineering or sre-reliability-engineering; pass startup/drain contract, resource limits, candidate identity, and runtime observations. |
Handoffs are needed only when that decision is open. They do not require loading every neighboring skill.
Completion
Report the changed behavior, the violated or protected invariant, relevant verification, and material limits. For a review, lead with findings tied to a concrete path, consequence, correction, and evidence. Never equate a resolved Promise, successful stream finish, local socket write, or returned HTTP response with durable external completion.
1---2name: node-typescript-backend-engineering3description: Build, review, and debug Node.js/TypeScript backend services, including async lifecycle, streams, workers, Fastify/Express adapters, and runtime validation. Browser rendering belongs to web-frontend-engineering; HTTP/OpenAPI artifacts to api-contract-engineering; engine proof to database-engineering.4---56# Node and TypeScript Backend Engineering78Make accepted work bounded, observable, and owned through completion or failure. Preserve the application's framework and module choices unless changing them solves the requested problem.910## Working Loop1112For a small fix, inspect the affected path and use the relevant reference. For broader implementation or review, trace:13141. **Runtime and module boundary.** Identify the deployed Node version, package manager, actual start command, module format, emitted artifact, and dependency initialization owner.152. **One terminal outcome.** Trace input through the handler or task to its result, error, timeout, or cancellation. Separate caller completion from the actual domain effect; an abandoned response does not prove a write failed.163. **Admission and cancellation.** Locate the constrained resource and its queue owner. Bound waiting and running work, include queue time in deadlines, propagate cancellation, and assign cleanup and late-result handling.174. **Stream or worker handoff.** Preserve backpressure, framing, data ownership, task identity, and terminal cleanup. Ordinary `async` code does not offload CPU work.185. **Validation and serialization.** Verify the actual parser, validator, handler input, response serializer, and framework scope. Type inference is a separate assurance.196. **Drain and evidence.** Stop admission, settle or reconcile accepted work within a deadline, release resources, and verify the affected failure path as well as success.2021Do not expand a routine endpoint change into a new architecture, pool, framework, or test harness without a demonstrated need.2223## Reference Routing2425Read only the material needed:2627- [Runtime, modules, and async contracts](references/runtime-modules-and-async-contracts.md): loader failures, event-loop stalls, async races, readiness, terminal ownership, messaging adapters, and graceful drain.28- [Streams, backpressure, and cancellation](references/streams-backpressure-and-cancellation.md): large inputs, framing, slow consumers, stream topology, and partial completion.29- [Workers and bounded capacity](references/workers-and-bounded-capacity.md): CPU offload, task queues, clone/transfer/share semantics, correlation context, and worker failure.30- [Fastify and Express HTTP lifecycle](references/fastify-express-http-lifecycle.md): hook and middleware placement, terminal response ownership, schemas, type providers, serialization, and transport boundaries.31- [Testing and packaging](references/testing-and-packaging.md): `node:test`, fixture ownership, mock isolation, actual package loading, and focused verification.32- [Reference index and source scope](references/00_README.md): provenance and version-sensitive refresh guidance.3334## Ownership and Handoffs3536This skill implements Node runtime adapters, request/task lifecycle, transaction use, and actual domain effects.3738| Unresolved decision | Primary owner and handoff |39| --- | --- |40| Observable HTTP/OAS/media/error or consumer compatibility | `api-contract-engineering`; pass operation identity, versions, expected contract, and actual request/response evidence. Implement the agreed adapter behavior here. |41| Distributed authority, delivery, durable idempotency, queue/log guarantees | `system-design`; pass effect boundary, task/message identity, timeout uncertainty, and failure window. |42| Event-time processing, pipeline publication, replay/backfill | `data-engineering`; pass source position, output/effect boundary, and observed completion state. |43| Engine constraints, isolation, locks, plans, or restore proof | `database-engineering`; retain connection/session and transaction cleanup here. |44| Browser state, React/Next rendering, server-client UI boundary | `web-frontend-engineering`. |45| General verification strategy or change lifecycle | `qa-testing` or `software-engineering`; retain Node runner, fixture, and package mechanics here. |46| Threat model and control design, or independent security verdict | `application-security-engineering` or `security-review`; implement the selected runtime controls here. |47| Deployment substrate or operated reliability | `platform-devops-engineering` or `sre-reliability-engineering`; pass startup/drain contract, resource limits, candidate identity, and runtime observations. |4849Handoffs are needed only when that decision is open. They do not require loading every neighboring skill.5051## Completion5253Report the changed behavior, the violated or protected invariant, relevant verification, and material limits. For a review, lead with findings tied to a concrete path, consequence, correction, and evidence. Never equate a resolved Promise, successful stream finish, local socket write, or returned HTTP response with durable external completion.
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