How client API calls are served in API Edge (ie., in Router or Message Processor) . In other words, Does all calls from clients are processed asynchoronsly in MP ?

[#1]

I understand that the API Traffic from Client app are handled through R (decides which MP to be considered for processing API). But nowhere i could found how the APIs are served i.e., will it be served synchronously OR asynchronously. If it is Asynch, how it is implemented in the MP/R, plz give little more explaination on how Asynch serving is done. Thanks