In MuleSoft API layers, which layer sits closest to backend systems?

In MuleSoft API layers, which layer sits closest to backend systems?

• A. System API
• B. Process API
• C. Experience API
• D. Data API

Answer: (A)

System API is the layer closest to backend systems. It connects directly to databases, ERP, CRM, and other legacy services using their native protocols, handling authentication and basic connectivity. This layer provides stable contracts and initial data shaping for downstream layers, shielding the rest of the API-led stack from backend changes and complexity. Process APIs sit above it, orchestrating calls to multiple System APIs to implement business workflows, while Experience APIs expose tailored, user-facing interfaces. The Data API is a specialized access pattern and may live within the stack, but the role closest to the backend is the System API.

System API is the layer closest to backend systems. It connects directly to databases, ERP, CRM, and other legacy services using their native protocols, handling authentication and basic connectivity. This layer provides stable contracts and initial data shaping for downstream layers, shielding the rest of the API-led stack from backend changes and complexity. Process APIs sit above it, orchestrating calls to multiple System APIs to implement business workflows, while Experience APIs expose tailored, user-facing interfaces. The Data API is a specialized access pattern and may live within the stack, but the role closest to the backend is the System API.