It's mitigated in several ways. But first of all consider that XMPP is hardly inefficient by today's standards, when mobile devices can stream video continuousl

It's mitigated in several ways. But first of all consider that XMPP is hardly inefficient by today's standards, when mobile devices can stream video continuously for hours on a single charge. Still, battery is important to consider, so what have we done in XMPP to improve energy efficiency in the past 15 years? One of the first things we did was define a way for clients to reconnect a session that suffered a broken connection - the classic "I just went through a tunnel" scenario. With this optimization we gained two things: a way to quickly reconnect without resynchronizing everything, and a guarantee that no traffic was lost in the process due to the network interruption. Secondly, we've implemented traffic optimization in servers. Clients will tell the server when they are idling in the background, and the server will stop sending any traffic that isn't time-sensitive. As soon as the user focuses the app, it tells the server and the connection switches back to "real-time" delivery. This behaviour helps keep network activity low when the client is in the background, and prevents continuously waking up the device's radio (such wake-ups can be quite power hungry over the course of a day). Finally, modern mobile XMPP clients support push notifications, which is the Apple/Google sanctioned way of solving this problem. It means that you can safely close the XMPP client entirely and still get notified when you receive messages. There's probably more besides these things that I've forgotten but I think these changes are the highlights!