Clean Architecture is not about folders, frameworks, or diagrams. It is about decisions. This book presents Clean Architecture as it truly exists in professional practice: a set of criteria for making conscious decisions about structure, dependencies, and the long-term evolution of software systems. Rather than treating architecture as a rigid or academic model, the author guides the reader through an approach grounded in technical responsibility, structural clarity, and domain protection. Each chapter connects architectural principles to real problems faced in production systems, avoiding dogmatism and artificial solutions. The book covers topics such as: architecture as a professional responsibility, - separation of layers without conceptual confusion, - dependency control, - the domain as the core source of value, - use cases as the heart of the application, - boundaries between application and infrastructure, - persistence, testability, and evolution without rewrites, - Clean Architecture in real-world systems, - its relationship with Domain-Driven Design (DDD), - common structural mistakes, - practical adoption and architectural consolidation, - Clean Architecture as a career differentiator. This is not a book about following rules blindly, but about developing architectural maturity. Its goal is to help professionals build clearer, more evolvable, and more sustainable systems, without requiring constant heroics or frequent rewrites. Recommended for developers, architects, and technical leaders who want to understand architecture as a continuous practice, not as a trend or a checklist.