Which three recommendations should be made?

An enterprise architect has requested the Salesforce Integration architect to review the following (see diagram & description) and provide recommendations after carefully considering all constraints of the enterprise systems and Salesforce platform limits.

• About 3,000 phone sales agents use a Salesforce Lightning UI concurrently to check eligibility of a customer for a qualifying offer.

• There are multiple eligibility systems that provides this service and are hosted externally. However, their current response times could take up to 90 seconds to process and return (there are discussions to reduce the response times in future, but no commitments are made).

• These eligibility systems can be accessed through APIs orchestrated via ESB (MuleSoft).

• All requests from Salesforce will have to traverse through customer’s API Gateway layer and the API Gateway imposes a constraint of timing out requests after 9 seconds.

Which three recommendations should be made? Choose 3 answers
A . ESB (Mule) with cache/state management to return a requestID (or) response if available from external system.
B. Recommend synchronous Apex call-outs from Lightning UI to External Systems via Mule and implement polling on API gateway timeout.
C. Use Continuation callouts to make the eligibility check request from Salesforce from Lightning UI at page load.
D. When responses are received by Mule, create a Platform Event in Salesforce via Remote-Call-In and use the empAPI in the lightning UI to serve 3,000 concurrent users.
E. Implement a ‘Check Update’ button that passes a requestID received from ESB (user action needed).