Clean Architecture in Practice

Clean Architecture has become a popular approach to structuring applications, but I often see teams struggle to apply it in practice. Here's how I approach it without falling into the over-engineering trap.

The Core Principle

At its heart, Clean Architecture is about dependency direction. Your business logic should not depend on external concerns like databases, frameworks, or UI. Instead, those external concerns should depend on your business logic.

UI -> Controllers -> Use Cases -> Entities
                  -> Repositories (interfaces)

Infrastructure implements Repositories

Practical Application

1. Start with Use Cases

Before writing any code, I define use cases. These are the actions your system can perform. Each use case:

• Has a clear input and output
• Contains business logic only
• Does not know about HTTP, databases, or frameworks

2. Define Ports

Ports are interfaces that your use cases need. They define what your application needs from the outside world without specifying how it's implemented.

Common ports include:

• Repository interfaces for data access
• Service interfaces for external APIs
• Event publishers for messaging

3. Implement Adapters

Adapters are the implementations of your ports. This is where framework-specific code lives:

• Database repositories
• HTTP controllers
• Message queue consumers

When to Apply It

Clean Architecture adds complexity. Use it when:

• Building applications that will live for years
• Working with complex business logic
• You need to support multiple interfaces (API, CLI, etc.)

For simple CRUD applications or quick prototypes, a simpler architecture might be more appropriate.

Conclusion

Clean Architecture is a powerful tool, but like any tool, it should be applied thoughtfully. Focus on the principles - dependency inversion and separation of concerns - rather than rigid adherence to a specific folder structure.