Author of JMAP here. * JMAP uses opaque ids rather than sequential ids, which makes a lot of this easier (the servers can ensure they have their own id namespac

Author of JMAP here. * JMAP uses opaque ids rather than sequential ids, which makes a lot of this easier (the servers can ensure they have their own id namespace to avoid collisions). * The resync mechanism (see the "/changes" method) just indicates something may have changed and then you fetch those records. It's definitely possible to make your master-master replication work so that /changes works regardless of which master you were previously talking to, at the expense of some loss of efficiency (you may end up refetching some data you actually already had).