GraphQL Learn

GraphQL — Learn Documentation

Official GraphQL learning documentation at https://graphql.org/learn/.

Unverified

The graphql.org site returned HTTP 403 during the fetch, so these notes are based on the gRPC and Richardson sources plus general knowledge of GraphQL. Content should be cross-checked against the live documentation if a detailed refresh is needed.

Summary

GraphQL is a query language for APIs and a server-side runtime developed by Facebook (open-sourced 2015). Clients describe the exact shape of data they need; the server resolves and returns precisely that. A single endpoint replaces multiple REST routes.

Key Concepts

• Operations: Query (read), Mutation (write), Subscription (real-time push via WebSocket).
• Type System: Scalar types (Int, Float, String, Boolean, ID), object types, interfaces, unions, enums, input types.
• Schema: The contract between client and server; all available types and operations are defined here.
• Resolvers: Server-side functions that return data for each field in the schema.
• Introspection: The schema is self-describing; tools like GraphiQL auto-generate docs and enable query completion.
• N+1 problem: Naive resolver implementations issue N database queries for N items; solved with DataLoader (batching).
• Fragments: Reusable field sets for composing queries.
• Variables: Parameterise queries at runtime without string interpolation.
• Directives: @deprecated, @skip, @include modify execution or schema documentation.

Wiki Pages That Cite This Source

• GraphQL — full concept page
• API Design Overview — GraphQL in the REST vs. GraphQL vs. gRPC comparison
• API Design Principles — versionless evolution, schema-driven backward compatibility