Backend Engineering Skill — Quick Reference

This skill equips backend engineers with execution-ready patterns for modern API development, database design, authentication, caching, observability, error handling, testing, and deployment. Apply these patterns when you need REST/GraphQL API design, database schema modeling, authentication flows, performance optimization, or production-grade backend architectures.

Modern Best Practices (December 2025): GraphQL adoption, TypeScript 5.9+ strict mode, TypeScript 7 native preview (Project Corsa) for faster tooling https://devblogs.microsoft.com/typescript/progress-on-typescript-7-december-2025/, unknown over any, structured logging, secret managers, and secure defaults (rate limiting, headers, input validation).

Quick Reference

When to Use This Skill

Use this skill when you need:

• REST or GraphQL API design and implementation (GraphQL adoption increasing)
• Database schema design and migrations (Prisma schema-first approach, Prisma Accelerate for serverless)
• Authentication and authorization patterns (JWT, OAuth2, sessions, NextAuth.js)
• Error handling and validation strategies (Zod/Joi TypeScript-first validation)
• API security best practices (Helmet.js headers, OWASP API Security Top 10, rate limiting)
• Performance optimization and caching (Redis, Prisma connection pooling, singleton pattern)
• Testing strategies (Vitest, Jest, Playwright for E2E, supertest for API testing)
• Background job processing (BullMQ, Agenda)
• API documentation and versioning (Swagger/OpenAPI auto-generation)
• Deployment and production readiness (PM2 process management, Docker, secret managers)
• Monitoring and observability (structured logging with Pino/Winston, Sentry, OpenTelemetry)

Decision Tree: Backend Technology Selection

Backend project needs: [API Type]
    ├─ REST API?
    │   ├─ Simple CRUD → Express 5.x + Prisma 6.x
    │   ├─ Enterprise features → NestJS 11.x (built-in DI, modules)
    │   └─ High performance → Fastify 5.2 (faster than Express)
    │
    ├─ GraphQL API?
    │   ├─ Code-first → Pothos GraphQL (TypeScript)
    │   └─ Schema-first → Apollo Server + GraphQL Codegen
    │
    ├─ Authentication Strategy?
    │   ├─ JWT tokens → jsonwebtoken + httpOnly cookies
    │   ├─ OAuth/Social → NextAuth.js or Passport.js
    │   └─ Magic links → Custom implementation + email service
    │
    ├─ Database Layer?
    │   ├─ Type-safe ORM → Prisma 6.x (best for TypeScript)
    │   ├─ SQL-first → Drizzle ORM or Kysely
    │   └─ Raw SQL → pg (PostgreSQL 18 driver)
    │
    ├─ Caching Strategy?
    │   ├─ Distributed cache → Redis (multi-server)
    │   ├─ Serverless cache → Upstash Redis
    │   └─ In-memory cache → Node.js Map (single server)
    │
    └─ Background Jobs?
        ├─ Complex workflows → BullMQ (Redis-backed, retries)
        └─ Simple scheduling → node-cron or Agenda

Language Alternatives:

• Node.js 24 LTS / 25 Current (Express 5.x / Fastify 5.2 / NestJS 11.x + Prisma 6.x): TypeScript-first, async/await, Web Storage API
• Python 3.14+ (FastAPI 0.115+ + SQLAlchemy 2.0+): Data-heavy services, async support, evolving concurrency model, modern typing
• Go 1.25+ (Fiber 2.x + GORM 1.25+): High concurrency, native performance, experimental encoding/json/v2
• Rust 1.92+ (Axum 0.8+ + SeaORM 1.1+): Memory safety, zero-cost abstractions, Rust 2024 edition

See templates/ for language-specific starter templates.

API Design Patterns (Dec 2025)

Idempotency Patterns

All mutating operations MUST support idempotency for retry safety.

Implementation:

// Idempotency key header
const idempotencyKey = request.headers['idempotency-key'];
const cached = await redis.get(`idem:${idempotencyKey}`);
if (cached) return JSON.parse(cached);

const result = await processOperation();
await redis.set(`idem:${idempotencyKey}`, JSON.stringify(result), 'EX', 86400);
return result;

Pagination Patterns

Prefer cursor-based pagination for APIs with frequent inserts.

Error Response Standard (Problem Details)

Use a consistent machine-readable error format (RFC 9457 Problem Details): https://www.rfc-editor.org/rfc/rfc9457

{
  "type": "https://example.com/problems/invalid-request",
  "title": "Invalid request",
  "status": 400,
  "detail": "email is required",
  "instance": "/v1/users"
}

Health Check Patterns

// Liveness: Is the process running?
app.get('/health/live', (req, res) => {
  res.status(200).json({ status: 'ok' });
});

// Readiness: Can the service handle traffic?
app.get('/health/ready', async (req, res) => {
  const dbOk = await checkDatabase();
  const cacheOk = await checkRedis();
  if (dbOk && cacheOk) {
    res.status(200).json({ status: 'ready', db: 'ok', cache: 'ok' });
  } else {
    res.status(503).json({ status: 'not ready', db: dbOk, cache: cacheOk });
  }
});

Migration Rollback Strategies

Optional: AI/Automation Extensions

Note: AI-assisted backend patterns. Skip if not using AI tooling.

AI-Assisted Code Generation

Review requirements for AI-generated code:

• All imports verified against package.json
• Type checker passes (strict mode)
• Security scan passes
• Tests cover generated code

Navigation

Resources

• resources/backend-best-practices.md — Node.js patterns for auth, error handling, database, performance, testing, observability
• resources/go-best-practices.md — Go idioms, concurrency, error handling, GORM usage, testing, profiling
• resources/rust-best-practices.md — Ownership, async, Axum, SeaORM, error handling, testing
• resources/python-best-practices.md — FastAPI, SQLAlchemy, async patterns, validation, testing, performance
• README.md — Folder overview and usage notes
• data/sources.json — External references per language/runtime
• Shared checklists: ../software-clean-code-standard/templates/checklists/backend-api-review-checklist.md, ../software-clean-code-standard/templates/checklists/secure-code-review-checklist.md

Shared Utilities (Centralized patterns — extract, don't duplicate)

• ../software-clean-code-standard/utilities/auth-utilities.md — Argon2id, jose JWT, OAuth 2.1/PKCE
• ../software-clean-code-standard/utilities/error-handling.md — Effect Result types, correlation IDs
• ../software-clean-code-standard/utilities/config-validation.md — Zod 3.24+, Valibot, secrets management
• ../software-clean-code-standard/utilities/resilience-utilities.md — p-retry v6, opossum v8, OTel spans
• ../software-clean-code-standard/utilities/logging-utilities.md — pino v9 + OpenTelemetry integration
• ../software-clean-code-standard/utilities/testing-utilities.md — Vitest, MSW v2, factories, fixtures
• ../software-clean-code-standard/utilities/observability-utilities.md — OpenTelemetry SDK, tracing, metrics
• ../software-clean-code-standard/resources/clean-code-standard.md — Canonical clean code rules (CC-*) for citation

Templates

• templates/nodejs/template-nodejs-prisma-postgres.md — Node.js + Prisma + PostgreSQL
• templates/go/template-go-fiber-gorm.md — Go + Fiber + GORM + PostgreSQL
• templates/rust/template-rust-axum-seaorm.md — Rust + Axum + SeaORM + PostgreSQL
• templates/python/template-python-fastapi-sqlalchemy.md — Python + FastAPI + SQLAlchemy + PostgreSQL

Related Skills

• ../software-architecture-design/SKILL.md — System decomposition, SLAs, and data flows
• ../software-security-appsec/SKILL.md — Authentication/authorization and secure API design
• ../ops-devops-platform/SKILL.md — CI/CD, infrastructure, and deployment safety
• ../qa-resilience/SKILL.md — Resilience, retries, and failure playbooks
• ../software-code-review/SKILL.md — Review checklists and standards for backend changes
• ../qa-testing-strategy/SKILL.md — Testing strategies, test pyramids, and coverage goals
• ../dev-api-design/SKILL.md — RESTful design, GraphQL, and API versioning patterns
• ../data-sql-optimization/SKILL.md — SQL optimization, indexing, and query tuning patterns

Operational Playbooks

• resources/operational-playbook.md — Full backend architecture patterns, checklists, TypeScript notes, and decision tables