Three Years of DDD in Practice: Insights from the Opening Chapter

Three years ago the CTO mandated that every microservice adopt Domain‑Driven Design (DDD). With only a superficial understanding from a few articles, the author bought Eric Evans' and Vaughn Vernon's books, studied numerous blogs, and began experimenting in the codebase.

During this period the team hit many pitfalls: mis‑defining aggregate boundaries, blurring responsibilities between domain services and application services, and struggling with how MyBatis Plus maps value objects. Each issue was identified and resolved through hands‑on trial and error.

Now all microservices run on a unified DDD structure, allowing any team member to follow the same conventions. This column series documents those three years of experience, focusing on production‑ready code structures and design decisions rather than abstract theory.

The series takes a "code first" approach, starting from real database tables (order, allocation, receipt, statistics). From table fields and relationships it demonstrates how to identify aggregate roots, split sub‑entities, extract value objects, locate business rules, and organize cross‑module collaboration.

The column consists of 24 articles divided into seven modules:

Module 1 – Introduction (2 articles)

Module 2 – From Table to Aggregate (6 articles)

Module 3 – Layering and CQRS (4 articles)

Module 4 – Services and Orchestration (3 articles)

Module 5 – Bounded Contexts and Events (4 articles)

Module 6 – Practical Guidelines (3 articles)

Module 7 – Architectural Thinking (2 articles)

Each article walks through concrete code examples, such as designing an AggregateRoot base class, handling sub‑entities, extracting value objects, applying CQRS, defining domain services, and using hexagonal and clean architecture principles.

DDD has no single correct answer; the presented approach blends book‑based concepts with project‑specific trade‑offs discovered over three years. Readers can apply the same step‑by‑step method to refactor any module in their own Spring Boot + MyBatis Plus projects without rewriting code or changing frameworks.