Pretty basic. The receiving process usually has an input thread that just puts the messages into a queue. Then a processing thread processes (maybe logic, maybe

Pretty basic. The receiving process usually has an input thread that just puts the messages into a queue. Then a processing thread processes (maybe logic, maybe disk writes, maybe send) the messages and queues up periodic batch acks to the sender. The sender uses these acks to clear its own queue. The receiver persists the last acked sequence number, so that in case of a restart, it can tell upstream senders to restart sending messages from that point.