Understanding Domain-Driven Design: Value, Process, and Architectural Practices

In recent years the Tongtian Tower platform has matured to support most activities of the JD group, yet increasing personalized and non‑standard requirements have driven the creation of a technology‑oriented project called Tongtian Tower Blocks, which aims to provide an open front‑end SDK, flexible back‑end data sources, and a highly adaptable canvas for activity construction.

Facing complex block business logic and unpredictable changes, the team seeks a solution that decouples business from underlying technology; Domain‑Driven Design (DDD) emerges as a promising approach.

DDD Value

Handling Complex Business

Complexity stems from both business and technical requirements. Business complexity grows with the number and hierarchy of requirements, while technical complexity arises from quality demands such as security, performance, high availability, and scalability. DDD separates business logic from technical implementation, keeping them orthogonal.

Through layered and hexagonal architectures, DDD isolates business concerns, allowing any technology to be swapped without affecting core domain rules.

Rapid Response to Business Changes

DDD encourages focusing on the core problem domain, using bounded contexts and context maps to decompose a large system into independent, cohesive sub‑domains, thereby reducing the impact of change.

Synergy with Microservices

Microservice characteristics—high cohesion, loose coupling, independent deployment—align with DDD’s bounded contexts. Strategic design defines contexts; tactical design provides the concrete models, enabling microservices to be built on solid domain foundations.

Supporting Mid‑Platform Strategy

DDD promotes a unified language among domain experts and developers, improves collaboration, and delivers stable, extensible systems that can evolve without massive rewrites.

DDD Process

DDD consists of two main phases: strategic design and tactical design.

Strategic Design

Refining the Problem Domain

Domain experts and developers collaborate to analyze requirements, extract knowledge, and create a ubiquitous language, then identify core, generic, and supporting sub‑domains.

Identifying Bounded Contexts

Bounded contexts act as autonomous units with clear boundaries, enabling independent evolution and clear integration patterns.

Context Mapping

Defines how bounded contexts interact (e.g., Open Host Service, Anti‑Corruption Layer) and supports microservice collaboration.

Tactical Design

Domain Model Elements

Entity : objects with identity.

Value Object : immutable objects without identity.

Aggregate : cluster of entities/value objects with a root.

Domain Service : operations that don’t naturally belong to an entity or value object.

Repository : abstraction for persisting aggregates.

Factory : encapsulates complex object creation.

Module : logical grouping of related concepts.

Domain Primitive

Rich value objects that encapsulate validation and behavior, turning implicit concepts (e.g., activity type) into explicit, testable objects.

In summary, DDD is not a framework but a methodology for modeling complex domains; its successful adoption requires deep collaboration between domain experts and developers, disciplined strategic and tactical design, and careful architectural choices such as layered, hexagonal, or clean architecture to keep business logic stable while allowing technical evolution.