Clean Architecture in NestJS — A Practical Guide

Building NestJS apps is easy. Building NestJS apps that are still easy to change six months later is a different story. Clean Architecture gives you a way to structure your code so that business logic doesn't bleed into HTTP handlers, database queries don't dictate your domain model, and swapping infrastructure (say, Postgres → SQLite, or REST → gRPC) doesn't require rewriting half the app. This guide is practical. We'll build a small feature — managing User entities — and walk through each layer with real code. The core idea Clean Architecture revolves around one rule: dependencies point inward. ┌──────────────────────────────────┐ │ Infrastructure │ HTTP, DB, external APIs │ ┌──────────────────────────┐ │ │ │ Application │ Use cases / orchestration │ │ ┌──────────────────┐ │ │ │ │ │ Domain │ Entities, ports │ │ └──────────────────┘ │ │ │ └──────────────────────────┘ │ └──────────────────────────────────┘ Domain — pure business logic, no framework dependencies Application — use cases