It feels a bit misleading to say PostGraphile is "GraphQL-as-a-Service". Typically XaaS is used when there's an external service (normally hosted elsewhere) that provides this functionality; whereas PostGraphile is 100% self-hosted, we do not even have a hosted offering. Further, PostGraphile is more of a framework for building a GraphQL API than a separate service you run - since it's pure JS (well, TypeScript) a decent portion of our users mount PostGraphile directly into their Express or Koa applications and deeply integrate it, including customising and extending it via plugins. It's much more of a library/framework than an "-as-a-service". (I'm the PostGraphile maintainer.)