Event driven Kubernetes service

Im looking for an inter-service communication solution.

I have 1 service and multiple pods with an incoming gRPC stream. The initial request calls out to an external resource which eventually triggers a request back to this service with a status message. This is on a separate thread and for this example ends up going to Pod B. I would like PodA to respond with this status message. I have tried to demonstraite this with the workflow below.

The obvious solution here is to add some sort of messaging pattern but I would am looking for help in determining which is the best approach. The example below introduces a service mesh sidecar which would route external requests to a queue which Pod A would then subscribe to. If using AMQP, I would probably look to use direct exchange.

Any further information needed, please let me know. Thanks in advanced.