O'Reilly Domain-Driven Transformation: Modernize Legacy Systems and Mitigate Risk

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 Carola Lilienthal and Henning Schwentner 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