Clean Architecture

Clean Architecture keeps business rules separate from delivery and infrastructure details. Your application still uses a web framework, database, message broker, or command line. Those tools sit outside the policy that defines what the application does.

The central idea is a direction rule. Source code dependencies point toward business policy. Inner code does not name outer tools. Outer code translates between a tool's format and the application's own models.

This structure gives you options. You can test business behavior without starting a web server or connecting to a production database. You can replace a user interface or persistence mechanism without rewriting the core rules. The architecture does not remove change. It limits how far a change can spread.

Why boundaries matter

Applications often begin with a framework-generated structure. Controllers receive requests. Data-access objects store records. Business decisions then slip into both places because they are convenient.

That arrangement works until one decision must serve another interface or use another storage mechanism. The same rule gets copied, or the new interface must call through the old delivery path. Tests also inherit setup that has nothing to do with the rule under test.

Clean Architecture draws explicit boundaries around policy. A boundary controls which concepts cross and which direction the code knows about. It separates reasons to change:

• Business rules change when the organization changes its policy.
• Application rules change when a use case changes.
• Interface adapters change when an external format changes.
• Frameworks and drivers change when a technical product changes.