It's highly customisable, works directly with postgresql row levels security and the performance is quite good. It has a custom GraphiQL gui to work on queries/mutations.

To really see how it all works together checkout the starter project: https://github.com/graphile/starter it has migrations, job queue, graphql-codegen etc.

Benjie (https://github.com/benjie) is one of the greatest maintainers I've ever seen!