The toy example with two nodes incrementing and decrementing likes independently and then sharing the delta with each other would require an increasing amount of backend requests (n^2) for every like. If you had 10000 nodes and they were all sending 9999 requests to eachother for a single request, obviously that's not the best model. It did somewhat remind me of MySQLs active-active replication scheme but that has some locking to make sure drift isn't too bad. MySQL Group Sync also doesn't scale beyond 9 nodes.