Domain-driven Design (DDD) continues to shape how modern software systems are built by bridging the gap between technical teams and business needs. Its emphasis on modeling the domain with precision and clarity is especially relevant in today's fast-paced, complex software landscape. This book begins with DDD fundamentals, including core principles, a shared language, and the distinction between strategic and tactical approaches, progressing to strategic concepts like bounded contexts, context mapping, and domain events. It explores the tactical Java implementation detailing entities, value objects, services, aggregates, and repositories. The book also explores testing strategies and architectural validation using ArchUnit/jMolecules. Further, it explores DDD across microservices, monoliths, and distributed systems, integrating with Clean Architecture and SQL/NoSQL data modeling to prevent impedance mismatch. It thoroughly covers applying DDD within Jakarta EE, Spring, Eclipse MicroProfile, and Quarkus. By the end, you will be equipped to model business logic more effectively, design systems that reflect real-world domains, and integrate DDD seamlessly into enterprise applications. You will gain clarity, confidence, and the tools needed to build software that delivers business value. WHAT YOU WILL LEARN ¿ Apply DDD from strategic to tactical design. ¿ Model aggregates, entities, and value objects in Java. ¿ Use DDD in monoliths, microservices, and distributed systems. ¿ Integrate DDD with Spring and Jakarta EE frameworks. ¿ Apply Clean Architecture principles alongside DDD. ¿ Structure data modeling for SQL and NoSQL systems. ¿ Apply bounded contexts, context mapping, and domain events for architecture. WHO THIS BOOK IS FOR This book is ideal for Java developers, software architects, tech leads, and backend engineers. It is especially valuable for professionals designing scalable enterprise systems or applying DDD in modern software architecture.