A while ago I talked to some team that was planning a migration to GraphQL, long after this was generally thought to be a bad idea. The lead seemed really attached to the "composable RPCs" aspect of the thing, and at the time it seemed like nothing else offered this. It would be quite cool if capnproto became a more credible option for this sort of situation. At the time users could read about the rpc composition/promise passing/"negative latency" stuff, but it was not quite implemented.