Facebook has been using GraphQL in production for almost four years; today, it serves over 300 billion queries a day and its schema has nearly 10,000 types. In building this API, we’ve developed a set of best practices for designing an understandable and scalable GraphQL schema. Based on real examples in Facebook’s production GraphQL API, we'll discuss common GraphQL patterns, how they differ from other best practices, and their implications on server and client design.