The Ruby on Rails framework boosts productivity by leveraging the convention-over-configuration principle and model-view-controller (MVC) pattern, enabling developers to build features efficiently. This initial simplicity often leads to complexity, making a well-structured codebase difficult to maintain. Written by a seasoned software engineer and award-winning contributor to many other open-source projects, including Ruby on Rails and Ruby, this book will help you keep your code maintainable while working on a Rails app. You’ll get to grips with the framework’s capabilities and principles to harness the full potential of Rails, and tackle many common design problems by discovering useful patterns and abstraction layers. By implementing abstraction and dividing the application into manageable modules, you’ll be able to concentrate on specific parts of the app development without getting overwhelmed by the entire codebase. This also encourages code reuse, simplifying the process of adding new features and enhancing the application's capabilities. Additionally, you’ll explore further steps in scaling Rails codebase, such as service extractions. By the end of this book, you’ll become a code design specialist with a deep understanding of the Rails framework principles.