Ask HN: Is anyone using GraphQL in production with a small team?

I know FB is using GraphQL in production, and I keep seeing it pop up more often; even with some references to it as "the REST killer" (which seems a bit hyperbolic). I'm more specifically interested to see if any smaller teams are using it and their results. I have an application with data relationships where it particularly seems to make sense.

From what I can see it's very well explained from the clients side (which makes sense), however, less so on the backend. I'm curious as to where you're finding best practices, performance implications, development time (vs REST), maturity, and do you enjoy using it? Any other benefits (besides the obvious) and any experiences with the Ruby implementation (graphql-ruby and libgraphqlparser gems) or Golang implementation would be appreciated as well.