hexagonal-architecture

Hexagonal architecture (Ports and Adapters) keeps business logic independent from frameworks, transport, and persistence details. The core app depends on abstract ports, and adapters implement those ports at the edges. Use this skill when the request involves boundaries, domain-centric design, refactoring tightly coupled services, or decoupling application logic from specific libraries. Outbound port interfaces usually live in the application layer (or in domain only when the abstraction is truly domain-level), while infrastructure adapters implement them. Dependency direction is always inward: Define a single use case with a clear input and output DTO. Keep transport details (Express req , GraphQL context , job payload wrappers) outside this boundary. Identify every side effect as a port: Ports should model capabilities, not technologies. Use case class/function receives ports via constructor/arguments.