I've been looking at the Django source code on syndication. I understand functionally what these feeds are and what they do but I'm not sure how the magic happens.
What is Django doing under the hood to send these changes out across the wire? Is Django just creating an object (like an XML file) the Client reads and not even using the network? What mechanism is employed to ensure users get those updates in a 'reasonable' amount of time - is it a combination of the browser (or some other software) knowing to go look for updates while Django diligently adds data to a file, or does Django do most of the work?
There's no magic, and Django does not do anything to even try to ensure clients get updates in any particular amount of time.
Feeds, like almost everything on the web, are an entirely pull-based mechanism. Feed readers are responsible for periodically requesting updates from the client.