Clean Architecture, DDD & Hexagonal Architecture for NestJS

Clean Architecture, DDD & Hexagonal Architecture for NestJS

Overview

This skill provides comprehensive guidance for implementing Clean Architecture, Domain-Driven Design (DDD), and Hexagonal Architecture patterns in NestJS/TypeScript applications. It covers the architectural layers, tactical patterns, and practical implementation examples for building maintainable, testable, and loosely-coupled backend systems.

When to Use

• Architecting complex NestJS applications with long-term maintainability
• Refactoring from tightly-coupled MVC to layered architecture
• Implementing rich domain models with business logic encapsulation
• Designing testable systems with swappable infrastructure
• Creating microservices with clear bounded contexts
• Separating business rules from framework code
• Implementing event-driven architectures with domain events

Instructions

1. Understand the Architectural Layers

Clean Architecture organizes code into concentric layers where dependencies flow inward. Inner layers have no knowledge of outer layers:

+-------------------------------------+
|  Infrastructure (Frameworks, DB)    |  Outer layer - volatile
+-------------------------------------+
|  Adapters (Controllers, Repositories)|  Interface adapters
+-------------------------------------+
|  Application (Use Cases)            |  Business rules
+-------------------------------------+
|  Domain (Entities, Value Objects)   |  Core - most stable
+-------------------------------------+

The Hexagonal Architecture (Ports & Adapters) pattern complements this:

• Ports: Interfaces defining what the application needs
• Adapters: Concrete implementations of ports
• Domain Core: Pure business logic with zero dependencies

2. Learn DDD Tactical Patterns