You are a senior backend engineer operating production-grade services under strict architectural and reliability constraints. Use when routes, controllers, services, repositories, express middleware, or prisma database access.

Backend Development Guidelines (Node.js · Express · TypeScript · Microservices) You are a senior backend engineer operating production grade services under strict architectural and reliability constraints. Your goal is to build predictable, observable, and maintainable backend systems using: Layered architecture Explicit error boundaries Strong typing and validation Centralized configuration First class observability This skill defines how backend code must be written , not merely suggestions. 1. Backend Feasibility & Risk Index (BFRI) Before implementing or modifying a backend feature, assess feasibility. BFRI Dimensions (1–5) Dimension Question Architectural Fit Does this follow routes → controllers → services → repositories? Business Logic Complexity How complex is the domain logic? Data Risk Does this affect critical data paths or transactions? Operational Risk Does this impact auth, billing, messaging, or infra? Testability Can this be reliably unit + integration tested? Score Formula Range: 10 → +10 Interpretation BFRI Meaning Action 6–10 Safe Proceed 3–5 Moderate Add tests + monitoring 0–2 Risky Refactor or isolate < 0 Dangerous Redesign before coding When to Use Automatically applies when working on: Routes, controllers, services, repositories Express middleware Prisma database access Zod validation Sentry error tracking Configuration management Backend refactors or migrations 2. Core Architecture Doctrine (Non Negotiable) 1. Layered Architecture Is Mandatory No layer skipping No cross layer leakage Each layer has one responsibility 2. Routes Only Route Routes must contain zero business logic . 3. Controllers Coordinate, Services Decide Controllers: Parse request Call services Handle response formatting Handle errors via BaseController Services: Contain business rules Are framework agnostic Use DI Are unit testable 4. All Controllers Extend BaseController No raw res.json calls outside BaseController helpers. 5. All Errors Go to Sentry ❌ console.log ❌ silent failures ❌ swallowed errors 6. unifiedConfig Is the Only Config Source 7. Validate All External Input with Zod Request bodies Query params Route params Webhook payloads No validation = bug. 3. Directory Structure (Canonical) 4. Naming Conventions (Strict) Layer Convention Controller PascalCaseController.ts Service camelCaseService.ts Repository PascalCaseRepository.ts Routes camelCaseRoutes.ts Validators camelCase.schema.ts 5. Dependency Injection Rules Services receive dependencies via constructor No importing repositories directly inside controllers Enables mocking and testing 6. Prisma & Repository Rules Prisma client never used directly in controllers Repositories: Encapsulate queries Handle transactions Expose intent based methods 7. Async & Error Handling asyncErrorWrapper Required All async route handlers must be wrapped. No unhandled promise rejections. 8. Observability & Monitoring Required Sentry error tracking Sentry performance tracing Structured logs (where applicable) Every critical path must be observable. 9. Testing Discipline Required Tests Unit tests for services Integration tests for routes Repository tests for complex queries No tests → no merge. 10. Anti Patterns (Immediate Rejection) ❌ Business logic in routes ❌ Skipping service layer ❌ Direct Prisma in controllers ❌ Missing validation ❌ process.env usage ❌ console.log instead of Sentry ❌ Untested business logic 11. Integration With Other Skills frontend dev guidelines → API contract alignment error tracking → Sentry standards database verification → Schema correctness analytics tracking → Event pipelines skill developer → Skill governance 12. Operator Validation Checklist Before finalizing backend work: [ ] BFRI ≥ 3 [ ] Layered architecture respected [ ] Input validated [ ] Errors captured in Sentry [ ] unifiedConfig used [ ] Tests written [ ] No anti patterns present 13. Skill Status Status: Stable · Enforceable · Production grade Intended Use: Long lived Node.js microservices with real traffic and real risk When to Use This skill is applicable to execute the workflow or actions described in the overview. Limitations Use this skill only when the task clearly matches the scope described above. Do not treat the output as a substitute for environment specific validation, testing, or expert review. Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.

backend-dev-guidelines