As protoetc mentioning, cpp-serializers contains so many projects, msgpack and the github org is like JSON, but very fast and small, that is not heavy like protobuf.
If project do not depends on grpc, and want to keep light, we can use rpclib. And msgpack is used in Ray.
When I survey QEMU + SystemC solution, I find the qbox, that use the rpclib. I need to investigate how to use it and where.ssss