Its a good time to ask, is gRPC any good? I'd love to standardize on stable middleware layer that handles multiple versions of clients and servers well. Rest with json really seems to work great for most things already.

What is the advantage of gRPC - just more efficient?

I found gRPC to be a bit too heavyweight and complex. I'm pretty excited about twirp[1] right now.

[1]: https://github.com/twitchtv/twirp