I've never connected this to the CAP theorem, it's a good way of looking at it. I see it as 2 different questions, "Did the computer hear me" and "Does the com

I've never connected this to the CAP theorem, it's a good way of looking at it. I see it as 2 different questions, "Did the computer hear me" and "Does the computer have a response for me.". Most people only make an effort to answer the latter for the user, it indirectly answers the first question anyways. But you can easily answer the first by quickly doing some sort of update, such as a progress indicator, animating a button staying depressed, etc. You don't have to mess with your real model until you get a response (or an error), but then you also don't leave the user confused for 12 seconds while your app loads search results or whatever. Obviously it doesn't work in every situation. In most video games you want your actions to affect the gameworld immediately, even if the server doesn't know about it yet. However, for most applications just adding fast indicators that the client is aware of your actions (and staying off the UI thread) will make it feel more responsive.