Yes, we also constantly think about that! In the document collections of UKV, for example, we have interoperability between JSON, BSON, and MessagePack objects [1]. CSV is another potential option, but text-based formats aren't ideal for large scale transmissions.
One thing people do - use two protocols. That is the case with Apache Arrow Flight RPC = gRPC for tasks, Arrow for data. It is a viable path, but compiling gRPC is a nightmare, and we don't want to integrate it into our other libraries, as we generally compile everything from sources. Seemingly, UJRPC can replace gRPC, and for the payload we can continue using Arrow. We will see :)
Are there any synergies with capnproto [1] or is the focus here purely on huge payloads?
I'm just an interested hobbyist when it comes to performant RPC frameworks but had some fun benchmarking capnproto for a small gamedev-related project and it was pretty awesome.
One thing people do - use two protocols. That is the case with Apache Arrow Flight RPC = gRPC for tasks, Arrow for data. It is a viable path, but compiling gRPC is a nightmare, and we don't want to integrate it into our other libraries, as we generally compile everything from sources. Seemingly, UJRPC can replace gRPC, and for the payload we can continue using Arrow. We will see :)
[1]: https://github.com/unum-cloud/ukv/blob/main/src/modality_doc...