domain-driven-design

Type-driven design uses types and sum types to make illegal states unrepresentable, catching errors at compile time. Model your domain concepts—like payment status or order states—as types that enforce valid transitions, reducing bugs and eliminating defensive checks throughout your codebase.

Ubiquitous language is consistent terminology shared between code, documentation, and business conversations. It reduces ambiguity, aligns developers and domain experts, and ensures your codebase accurately reflects business concepts, making maintenance and collaboration easier.

Entities have identity and lifecycle; value objects are immutable and defined by their attributes; aggregates group related entities around a root entity that manages consistency. This layered structure organizes domain logic, clarifies responsibilities, and prevents invalid state transitions across your models.

Yes. Generate Mermaid, Graphviz/DOT, or ASCII diagrams to visualize domain entities, state transitions, and workflows. Visual representations help teams align on complex domain structures and serve as executable documentation alongside your code.

The functional core/imperative shell pattern isolates pure domain logic (functional core) from side effects and I/O (imperative shell). This separation makes domain behavior testable, reusable, and independent of framework or database choices.

Use domain-driven design when complexity, invalid states, or inconsistent terminology cause bugs and maintenance friction. It's especially valuable for business-critical domains—e-commerce, banking, workflows—where precision and clarity directly impact system reliability and team communication.