Streaming HTTP and gRPC support is on our roadmap, but it's still a ways out :(
On the comment about how the control plane APIs support gRPC: the serving infrastructure for the data plane is pretty different from the control plane, so it's unfortunately not a direct map to supporting gRPC on the data plane.
Another possible solution is to run an API gateway that does gRPC to JSON conversion and have that invoke your service.
My understanding is that the major issue we have is with streaming (sticky sessions to backends that are autoscaling is tricky), so I assume that unary would be easier. I admit that I haven't dived too deeply in to this though.
EDIT: looks like we could do unary gRPC if gRPC wasn't only supported on HTTP/2. So the current implementation basically requires we solve sticky sessions/streaming.
We don't support inbound gRPC/streaming, but we do support outbound gRPC/streaming, so things like Firestore (or other streaming gRPC products) will work fine.
On the comment about how the control plane APIs support gRPC: the serving infrastructure for the data plane is pretty different from the control plane, so it's unfortunately not a direct map to supporting gRPC on the data plane.
Another possible solution is to run an API gateway that does gRPC to JSON conversion and have that invoke your service.