convention-solid-isp

The Interface Segregation Principle (ISP) states that clients should not depend on interfaces they do not use. It solves the problem of monolithic contracts by splitting large interfaces into focused, client-specific ones to minimize coupling and improve system maintainability.

To split a large API interface, refactor monolithic contracts into small, cohesive interfaces tailored to specific client responsibilities. Ensure implementations depend only on the relevant contracts, like separating Reader, Writer, and Validator interfaces so clients only use necessary parts.

Apply interface segregation in clean architecture when designing APIs, plugin architectures, or service interfaces to reduce unused methods. It is needed when fat interfaces cause tight coupling, requiring cohesive, minimal interfaces and explicit client-bound dependencies to support dependency injection.

Yes, interface segregation improves testability in service interfaces by reducing the surface area and dependencies. By ensuring clients depend only on focused, cohesive interfaces they actually use, implementations become easier to mock, read, and maintain during testing.

The best way to reduce coupling in a monolithic plugin architecture is to split large interfaces into focused, client-specific contracts. This approach minimizes unused methods and ensures teams depend only on explicit, client-bound dependencies, improving overall maintainability.