A couple of things I omitted for brevity:

The async server response doesn't contain the data. It contains a link to retrieve the data. So make a request and then wait to for a link to be sent to your server that you can use to retrieve the data for a limited time.

The responses sent to the server don't correspond one to one to the requests. One response may contain data for many requests, and many responses may contain data for one request. Each response contains data for many UATs.