[JonathonW]

Yeah, we've been pretty happy with protobuf in the projects where we've used it.

Cap'n Proto would've been a pretty strong contender if it had existed when we started using protobuf, though. Serialization/deserialization was on the critical path for our server-side code, so we most likely would have been able to get at least a bit of a performance boost out of Cap'n Proto.