architecture-paradigm-hexagonal

# The Hexagonal (Ports & Adapters) Paradigm ## When To Use - Isolating business logic from external dependencies - Systems needing swappable adapters for testing ## When NOT To Use - Small scripts or utilities without external dependencies - Prototypes where port/adapter abstraction adds overhead ## When to Employ This Paradigm - When you anticipate frequent changes to databases, frameworks, or user interfaces and need the core domain logic to remain stable. - When testing the core application requires mocking complex or slow infrastructure components. - When the development team needs to provide clear inbound and outbound interfaces for third-party integrations. ## Adoption Steps 1. **Define Domain Ports**: Identify all interactions with the core domain. Define inbound "driver ports" for actors that initiate actions (e.g., UI, CLI, automated jobs) and outbound "driven ports" for services the application consumes (e.g., database, message bus, external APIs). Express these ports as formal interfaces. 2. **Implement Adapters at the Edge**: For each external technology, create an "adapter" that implements a port's interface. Keep the core domain entirely ignorant of the specific frameworks or libraries used in the adapters. 3. **Aggregate Use Cases**: Organize the application's functionality into services that are built around business capabilities. These services orchestrate calls to the domain through the defined ports. 4. **Implement Contract Testing**: validate that e...