The biggest "relevant" problem with REST APIs here is the clients need to communicate with multiple data API endpoints. REST APIs require clients to do multiple network round-trips to get their data. They are usually a collection of endpoints where each endpoint represents a resource, so when a client needs data about multiple resources it needs to perform multiple network requests to a REST API and then put together the data it needs by combining multiple responses. In a pure REST API (not a customized one), a client cannot specify which fields to select for a record in that resource. That information is in the REST API service itself and the REST API service will always return all of the fields regardless of which ones the client actually needs. GraphQL’s term for this problem is over-fetching of information that is not needed. It is a waste of network and memory resources for both the client and the server. GraphQL speaks to the data as a graph and data is naturally a graph. If you need to represent any data, the right structure is a graph. The GraphQL runtime allows us to represent our data with a graph API that matches the natural graph shape of that data.

https://graphql.org/