🔺 GraphQL Flashcards
Query language & runtime for APIs — fetch exactly what you need
💡 What is GraphQL?
A query language for APIs and a server-side runtime to fulfill queries using your existing data.
📐 Schema
Defines types and relationships: type, interface, union, enum, input, and scalar.
🔍 Queries
Read operations that specify the exact fields needed. Supports arguments, aliases, and fragments.
✏️ Mutations
Write operations to create/update/delete data. Can return updated objects with requested fields.
📡 Subscriptions
Real-time updates over WebSockets. Server pushes events to subscribed clients.
🧩 Resolvers
Functions that resolve a field’s value. Can call DBs, REST services, or other APIs.
🧱 Scalars & Custom Scalars
Built-ins: Int, Float, String, Boolean, ID. Add custom types like DateTime.
🧬 Fragments
Reusable field selections to reduce duplication across queries and mutations.
🗺️ SDL (Schema Definition Language)
Human-readable syntax to define types and operations, e.g., type Query { me: User }.
🛡️ Validation & Types
Queries validated against schema before execution; strong typing enables safe evolution of APIs.
🚀 Tooling
Apollo, GraphQL Yoga, Mercurius, graphql-js, Relay, Hasura, URQL, GraphiQL/Playground.
🧭 Best Practices
Pagination (cursor-based), batching & caching, data loaders, auth at resolver level, error masking, persisted queries.