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Building Scalable APIs with NestJS

Lessons learned from building production-grade APIs at Vozi — from validation pipelines to modular architecture.

February 1, 2025
NestJS
Backend
Architecture

Building Scalable APIs with NestJS

When I started working at Vozi on the Drova platform, one of the first challenges was designing APIs that could scale with the business. Here's what I learned about building production-ready APIs with NestJS.

Why NestJS?

NestJS brings structure to Node.js backends. Coming from Express, where everything is a function, NestJS's opinionated approach with modules, controllers, and services felt restrictive at first — but it pays off at scale.

The module system forces you to think about boundaries. Each feature gets its own module, its own controller, its own service. When the codebase grows, you know exactly where to find things.

Validation Pipelines

One of the most impactful patterns is using class-validator with global validation pipes. Every request gets validated before it hits your business logic:

  • DTOs define the shape of incoming data
  • Decorators handle validation rules
  • Global pipes catch everything automatically

No more manual validation scattered across controllers.

Key Takeaways

  1. Structure matters — NestJS's module system prevents spaghetti code at scale
  2. Validate early — Use pipes and DTOs to catch bad data at the boundary
  3. Think in layers — Controllers handle HTTP, services handle logic, repositories handle data
  4. Document everything — Swagger integration makes your APIs self-documenting

The result? APIs that are easy to test, easy to understand, and easy to extend.