Which is NOT a role of an API proxy application running in a Mule runtime?

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

Answer: (B)

API proxies in Mule runtime are built to route requests to backend services, transform messages between the client and the backend, and enforce security policies at the edge. They handle forwarding the incoming request to the right backend, adapt the request or response payloads to match each side’s contract, and apply security controls like authentication, authorization, and rate limiting. What they don’t typically do is decide, based on the content of a backend response, which specific response is allowed to pass back to the client. The proxy forwards the backend’s response after applying any necessary transformations and policy checks, rather than filtering or selecting responses by content. So the role described in that option isn’t part of the standard duties of an API proxy. The other capabilities—routing, transforming, and enforcing security—fit squarely with the proxy’s responsibilities.