In part one, we developed a simple GraphQL server. That solution had one serious flaw: All fields were loaded eagerly on the back-end, even if they weren't requested by the front-end. We sort of accept this situation with RESTful services by not giving clients any choice.
RESTful API always returns everything, which implies always loading everything. If, on the other hand, you split RESTful API into multiple smaller resources, you risk N+1 problem and multiple network round trips. GraphQL was specifically designed to address these issues: