Have you used Mern.io in production yet?

Hi there, I was wondering if anyone used Mern in production already as I'm not yet clear about the production build and usage. It clearly says in the babel-register hook docs that it is not meant for production use, and yet Mern package.json starts index.js on "start:pro" script, which includes a babel-register hook. the build script seems to only refer to the client. What about the server? How do we build it? (es6 to es5) how do we start it in a production environment? Cheers Ajar