We are processing a realtime transaction (means that user swiped her card and is waiting on the "other" end for confirmation)
We put the data to Amazon MSK which basically puts the flow into async mode
Some microservice in Amazon EKS performs some actions and needs to "get back" to the waiting customer with approved/declined
How is that accomplished? Because if I understand correctly at some part (Transit Gateway?) the response "hangs" and the customer "waits". How does it get "notified" about the outcome?