layerwhere

LayerWhere is a conceptual framework used in software architecture to manage the placement of responsibilities across architectural layers. The term combines layer with where to emphasize the central question of where in the stack a capability should be implemented or consumed. It is a model rather than a specific technology, intended to guide decisions about boundary placement, responsibility distribution, and dependency direction within an application or system.

Core ideas include establishing clear layer responsibilities, enforcing locality constraints, and using mapping artifacts such as layer diagrams or layer maps. Practitioners specify which features belong to which layer—presentation, application, domain, data access, or infrastructure—and define allowed interactions between layers.

Applications of LayerWhere appear in enterprise software design, frontend–backend separation, and microservices ecosystems. It helps teams agree on ownership for a feature at a given layer, informs API design, and supports governance by documenting where changes should be made.

Benefits and limitations: by clarifying ownership and reducing cross-layer coupling, LayerWhere can improve maintainability, testability, and understanding. However, overly rigid boundaries can hinder evolution, and effective use depends on discipline, tooling, and organizational alignment.

History and context: LayerWhere arose as a practical reframing of layered architecture discussions, emphasizing the spatial question of responsibility rather than mere layering. It is widely used as a mental model in architecture reviews rather than as a formal standard.

See also: layered architecture, clean architecture, domain-driven design, software governance.