Creating Orchestration layer using Akka Stream

I’m exploring Akka Stream for a use case where I intend to replace heavy weight event bus (for event streaming) among fine grained components exposing REST based API within a single bounded context.While reading AKka stream documentation, I think this should be doable via flow mapAsynch stage. I don’t see any sample that invokes REST api via mapSynch stage within flow. has any one tried this? is this possible?

Any pointers would help and much appreciated.