If you can always merge reordered edits/messages then CAP does not apply because you don't need C (as defined in CAP), you may instead talk about partitions/con

If you can always merge reordered edits/messages then CAP does not apply because you don't need C (as defined in CAP), you may instead talk about partitions/connectivity issues as if they were some anomalous sources of large latencies in the system. You have your own, different definition of C. There are some very very large scale systems out there that work under the assumption that any edits can arrive reordered, and it's OK for the observable properties of the system. Here's what's "inconsistent" in an eventually consistent chat app: your typed responses might have been different had you seen in time what the other party has to say. To some degree the "computation" happens in your head. A "fully consistent" / "fully synchronous" chat app would sometimes refuse to send a message because the other party might have said something in the meantime. Like you'd expect from a fully-synchronous bank account balance handling system that wants to keep >= 0 balance at all times, rejecting overdraft transactions. (And I agree that this is completely acceptable behavior for a chat app; we as people are built to tolerate this kind of a problem in async person to person communication; just pointing out what does C in CAP exactly mean; the "fully synchronous" chat app would be just an occasional pain in the ass with little benefit)