Название: Domain-Driven Transformation: Modernize Legacy Systems and Mitigate Risk (Early Release) Автор: Carola Lilienthal, Henning Schwentner Издательство: O’Reilly Media, Inc. Год: 2025-07-11 Страниц: 123 Язык: английский Формат: epub Размер: 47.3 MB
Legacy systems slow down innovation, increase maintenance costs, and create misalignment between business goals and technical delivery. Domain-Driven Transformation offers a clear, risk-aware path to modernizing complex applications using principles from domain-driven design (DDD) and modular architecture. Authors Henning Schwentner and Carola Lilienthal guide software architects, technical leads, and senior engineers through practical, incremental strategies to evolve legacy systems without the disruption of a full rewrite.
With a focus on collaboration, modularity, and strategic refactoring, this book helps you assess architectural maturity using the modularity maturity index (MMI) and identify transformation opportunities through modeling techniques like event storming and domain storytelling. Packed with real-world examples and case-driven insights, you'll uncover the tools needed to build systems that scale, support business agility, and remain resilient over time.
• Assess your system’s modularity and architectural health with the MMI • Apply strategic and tactical DDD to manage complexity • Break apart monolithic systems into domain-aligned components • Use collaborative modeling techniques to align teams and clarify design Refactor incrementally with patterns that reduce risk while delivering value
Different software systems suffer from different “diseases” and we need a variety of remedies to cure them all. We have observed the following diseases in various combinations in legacy systems—whether monoliths or microservices—and their organizations in recent years:
• The legacy system has become a big ball of mud because no one controlled the dependencies and now everything is connected to everything else. • The domain knowledge is entangled into one huge domain model whose parts fit together only partially or even contradict each other. • Business source code and technical source code are mixed, and thus the replacement of obsolete technology or a domain extension becomes a Herculean task. • People are organized in a team structure that is unsuitable for making fast progress.
In this book, we present the treatments for these diseases that we have learned over the past 20 years working with Domain-Driven Design (DDD) and Legacy Software. These include: Refactorings, Domain Storytelling, EventStorming, Team Topologies and the Modularity Maturity Index (MMI). When we approach the healing in our projects and with our customers, we achieve that the respective development team looks significantly more positively into the future and motivation increases. The further the healing progresses, the happier our users, project leaders and managers will also be, because the stodgy and expensive legacy software becomes more stable, can be adapted more quickly and ultimately even allows innovative, forward-looking enhancements (again).
Our goal with this book is to provide you with means to help you divide up your software systems so that changes have as local an impact as possible. In this way, the individual software modules become manageable and understandable for the development teams again and can be processed by correspondingly small powerful teams. That is why you will find a number of source code examples in this book. The legacy systems we encounter are built in very different programming languages: Java, C#, PHP, C++ and many others. We have chosen to write the examples in the language that we encounter most frequently, i.e., Java. The examples are short enough that they should be understandable to programmers of other languages, and the procedure we describe is independent of the programming language.
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Domain-Driven Transformation (Early Release) 
