Which of the following is NOT a role of an API proxy in Mule runtime?

• A. Transform requests and responses
• B. Determine which response message is allowed to pass from the API backend service
• C. Enforce security policies
• D. Route traffic to backend services

Answer: (B)

The API proxy in Mule runtime serves as the gateway between clients and backend services, handling mediation tasks such as transforming payloads, routing requests to the correct backend, and enforcing security policies (authentication, authorization, rate limiting, etc.). It forwards responses from backends, potentially transforming them to match the API contract, but it does not decide which specific backend response messages are allowed to pass in a content-choice sense. That selection is not a typical role of the proxy; it’s handled by the backend or by policy logic applied at the edge. Therefore the statement about determining which response message is allowed to pass is not a standard responsibility of the API proxy.