Thanks for the reply. A Data Services real time service is accessed by sending messages to an Access Server, which has Job Servers running behind it. Each Job Server is running the same data flow, which takes an XML message in and replies with a resulting XML message. The Access Server automatically load balances the requests to as many Job Servers as you have configured, automatically starting and stopping them as the load requires. IMO, this is much better than just a REST call, which is why I use it.
Of course, if I can't get it to work, I can try REST calls as a fallback.
Thanks for the suggestion!