[mcheely]

It's not always as simple as a PUT landing. Imagine you're tracking something like a phone call in real time. You want to fetch the current state of the call and start tracking it, but it's changing relatively rapidly. You also don't want to have to push the full state of the call down the notification pipe on every update, because you're handling a lot of these.

Merging the incoming deltas with fetched API state becomes a bit tricky, because you have to account for changes that might be happening while your GET is in transit. Alternatively, it may be that your notifications are slower than the GET request, depending on network conditions. An option that works in both of these cases (and doesn't involve version tagging all of your assets) is the approach described in the blog post.