GraphQL

GraphQL is an API style in which the client specifies exactly which fields it wants, across as many related objects as it needs, and receives precisely that in a single response. Instead of many endpoints with fixed shapes, there is one endpoint and a typed schema describing everything available.

It earns its keep where several different clients need different slices of the same complex data — a web app, a mobile app and a partner integration, each with its own screens, one of them on a connection that cannot afford five round trips. The schema also gives strong tooling: types, autocompletion, and a form of documentation that cannot drift from the implementation.

The costs are real and they land on the server. Caching is harder than with REST because every query is different, and a deeply nested query can be expensive to answer, so query cost limits stop being optional. For a straightforward system with one client, it is usually more machinery than the problem justifies.