How we're trying to develop a new chat service through WebSockets at letgo coming from a monolithic REST API.
The challenge: Maintain the backwards compatibility. We don't want to force the mobile app users to update in order to use the new system. Furthermore, we have a lot of uncertainty on how the new system will perform, so in order to reduce it, we're taking advantage of an Event Sourcing approach in order to process in the new chat system in the staging environment the actual production load of the current system.
If you want to learn more about the whole process we've followed and not just the synchronization part, come to the Software Craftsmanship Barcelona! This time we (@SergiGP and me, @JavierCane, will try to explain some more interesting things about how we're trying to develop this new chat system and, maybe you could bring some interesting discussion points :D).
I'll do a video summarizing some of the talk conceptos for the http://codely.tv video blog, so stay tuned! http://twitter.com/CodelyTV