Why Mixing Business Logic Into React Components Hurts Long-Term Maintainability

Modern React projects often start fast but slow down as codebases grow, largely because business logic, API calls, and UI rendering get tangled together inside components. This architectural pattern, known as accidental coupling, makes testing harder, breaks unrelated features during refactors, and ties core business rules to framework-specific code. A checkout button example illustrates how a single component can simultaneously handle HTTP requests, shipping calculations, local storage, and rendering — creating fragile, hard-to-test code. When backend API schemas change, this tight coupling forces sweeping updates across many UI components at once. Clean architecture principles advocate separating domain logic from presentation layers to improve testability, stability, and framework independence.