Server Development / GraphQL
Fundamentals
A closer look at Fundamentals.
What is GraphQL
GraphQL is a typed query language for APIs: clients describe the shape of the data they need, and the server returns JSON that matches. This overview covers how requests flow from parse to execution, how responses differ from REST, and when a GraphQL layer is worth the complexity.
Schemas and SDL
A GraphQL schema is the contract between client and server: types, fields, and root operations written in Schema Definition Language or generated from code. This chapter explains SDL syntax, the Query/Mutation/Subscription roots, schema-first versus code-first workflows, and introspection.
Object types and scalars
Object types model entities with fields; scalars are the leaves that hold concrete values. This chapter covers built-in and custom scalars, enums, lists and non-null markers, interfaces, unions, and the __typename field clients use for polymorphism.
Input types and arguments
Arguments tune individual fields; input object types bundle structured write payloads. GraphQL keeps input and output types separate, which shapes how you design mutations, validate data, and avoid breaking clients when forms evolve.
Writing GraphQL operations
Operations are the queries, mutations, and subscriptions clients send. This chapter covers operation names, variables, aliases, reusable fragments, inline fragments for unions, and @include/@skip—patterns you will use in urql and codegen-backed apps.