interfacefirst

Interfacefirst is a software development approach that prioritizes the specification of interfaces before implementing their underlying behavior. The term is used to describe a discipline in API design, component software, and user interface development where contracts, data models, and interaction patterns are defined upfront to guide subsequent implementation.

In practice, interfacefirst involves creating formal interface specifications or contracts, such as API schemas, interface definitions in languages like TypeScript or Java, and mock implementations that simulate behavior. Teams use these contracts to drive parallel development, apply contract tests, and ensure interoperability across services or modules.

Benefits include improved collaboration across teams, clearer expectations, easier testing via contract tests, and greater decoupling between interface and implementation. Potential drawbacks include the overhead of up-front design, risk of over-specification, and the need for disciplined governance to prevent interfaces from becoming brittle as requirements evolve.

Interfacefirst can apply to different domains, including API design (contract-first development), UI/UX prototyping (defining user interactions before building visuals), and component-based architectures where modules are designed around well-defined interfaces. It is often discussed alongside related concepts such as contract-first development, interface-oriented design, and OpenAPI-driven workflows.

See also: API design, contract-first development, interface-oriented design, OpenAPI, microservices.