capnproto RPC actually supports some interesting features related to asynchronous execution: https://capnproto.org/rpc.html#time-travel-promise-pipelinin...

I'm surprised many people don't understand your comment - I had the same thoughts. gRPC provides a very nice way to describe event driven microservices using their "stream" keyword. It allows the implementation to be async, blocking, or future based. You get access to a very rich ecosystem such as bazel's grpc \ proto rules, junit rules, grpc-web for streaming to the browser, out of the box support from istio / envoy, etc.

You're right. My fault here. It should actually be possible to define a gRPC streaming API (never tried). The only missing thing for me is the protobuf compatibility though.

If you mean protobuf, here's a link to the discussion on why it wasn't included in v2.0.0. That said, we'll explore adding non-JSON formats (like XSD and protobuf) to the specicification this year.

you mean Protobuf or what exactly?

protobuf is just the serialization format gRPC is the replacement for HTTP and presumably asynchronous HTTP requests. Still not sure what their point is.