@willyaranda Well, a new device is coming online and doesn't have any channels registered. It's also quite possible that, Frankly, the server may not care what channelIDs are registered for the client. 

For my current implementation, my server doesn't sync state to the client. It accepts valid endpoints that resolve to UAID + ChannelIDs, and then passes them onto the client. This means that I don't have to keep state for millions of clients or do expensive data lookups for each submission.