To piggyback on this, is anyone using CBOR? They solve same problem as Protobuf, but more like JSON where a schema is not required.

Amazon uses CBOR extensively. Most AWS services by now should support being called using CBOR. The protocol they're using is publicly documented at: https://smithy.io/2.0/additional-specs/protocols/smithy-rpc-...

The services serve both CBOR and other protocols simultaneously.