Knowing that asynchronous drawbridges use message queues is only part of the problem. We still have to decide on these issues:
On the donor fortress side, what, exactly, will be technically responsible for inserting messages into the queue?
How will other workers inside the donor fortress communicate with the message inserter?
On the recipient fortress side, what, exactly, will be technically responsible for receiving the message? We know a guard will receive the message (because the message is being transferred across a trust boundary), but how will that guard be implemented?
How will other workers inside the recipient fortress receive their marching orders from the guard?
On the donor side, the envoy ...