when's it time to really think about a GraphQL API?

Hey folks, I've been seeing more and more about GraphQL lately, and while I get the benefits for frontend developers (single endpoint, client-specified data), I'm wondering about the backend implications. When does the added complexity of setting up and maintaining a GraphQL server become worth it compared to a well-designed REST API? Are there specific use cases or data shapes where it really shines? What are your experiences with implementing GraphQL on the backend?