Domain-Driven Design Fundamentals

Overview

Domain-Driven Design (DDD) aligns software structure with business domain concepts and language.

Key Building Blocks

• Bounded contexts
• Entities and value objects
• Aggregates
• Domain services and repositories

flowchart LR
    A[Bounded Context] --> B[Aggregate]
    B --> C[Entity]
    B --> D[Value Object]

Practical Example

In a billing context, Invoice can be an aggregate root while Money is a value object enforcing currency rules.

Production Example

Teams often split monolith modules by bounded contexts first, then evolve integration contracts between them before considering service extraction.

Common Pitfalls

• Applying DDD terminology without domain collaboration
• Oversized aggregates causing lock contention
• Ignoring ubiquitous language in code and docs

Key Takeaways

• DDD improves alignment between code and business logic.
• Bounded contexts reduce ambiguity and coupling.
• Collaboration with domain experts is essential.