Node.js Backend Fundamentals: Build Your First API
Event loop basics, Express structure, middleware patterns, and production habits for Node.js server development.
Node.js Architecture
Node runs JavaScript on the server using V8. Its event loop handles many concurrent connections with a single thread for I/O-bound work — ideal for APIs and real-time apps. CPU-heavy tasks should move to worker threads or external services.
npm ecosystems move fast. Lock files (package-lock.json) ensure reproducible installs across machines and CI.
Building a Simple API
Express remains the common starting framework: routes, middleware, JSON body parsing. Structure projects by feature or layer (routes → controllers → services → data access) before files sprawl.
Middleware handles cross-cutting concerns: logging, authentication, CORS, and error formatting. Order matters — error handlers come last.
Production Readiness
- Environment variables for secrets — never commit API keys.
- Input validation with zod or joi before touching the database.
- Structured logging (pino, winston) instead of console.log everywhere.
- Health check endpoints for load balancers and orchestrators.
Key Takeaways
- Node excels at I/O-bound APIs; offload CPU-heavy work elsewhere.
- Organize Express apps into layers before complexity grows.
- Middleware order and centralized error handling are non-negotiable.
- Secrets in env vars; validate all external input.