Interfaceswhere

Interfaceswhere is a term used in software architecture to describe the deliberate placement and management of interfaces across a system. The concept focuses on where interfaces are defined, exposed, and consumed—across user interfaces, APIs, contracts, and middleware surfaces—and how their location affects modularity, discoverability, and evolution of the system.

It encompasses both technical interfaces (API endpoints, library contracts, data schemas) and user-facing interfaces (web UIs, command-line tools, voice interfaces). The main concern is aligning interface surfaces with domain boundaries and deployment boundaries to minimize cross-cutting dependencies and to improve maintainability. In practice, interfaceswhere encourages documenting interface contracts, versioning strategies, and consistent discovery mechanisms.

Designers consider factors such as stable surface area, backward compatibility, clear ownership, and visibility for consumers. The term is sometimes used as a heuristic to evaluate whether a given interface is in the correct place relative to service boundaries, bounded contexts, or UI routes. It also calls for explicit discoverability, such as service registries, documentation, or UI component libraries.

While not widely codified in formal standards, interfaceswhere appears in some architectural writings and team discussions as a mental model for organizing interfaces. Proponents argue that it helps reduce coupling and accelerate change, while critics warn that the term may be ambiguous without precise definitions of what counts as an interface and where it should reside.

Related concepts include API design, interface contracts, modular architecture, service boundaries, and interface discoverability.