Web Development Intermediate

What is GraphQL?

A query language for APIs that lets clients request exactly the data they need, reducing over-fetching and under-fetching.

GraphQL, developed by Facebook, provides a single endpoint where clients specify their data requirements in queries. Unlike REST (multiple endpoints, fixed responses), GraphQL returns exactly what is requested — no more, no less.

Key concepts include schemas (type definitions), queries (read data), mutations (write data), and subscriptions (real-time updates). Tools include Apollo (client/server), Relay, and GraphiQL (interactive explorer). Trade-offs include complexity and caching challenges.

Related Terms

Server-Sent Events

A server push technology that enables a server to send real-time updates to a browser over a single HTTP connection.

An automatic OPTIONS request sent by browsers before certain cross-origin requests to check if the actual request is permitted.

API (Application Programming Interface)

A set of rules and protocols that allows different software applications to communicate and exchange data.

A JavaScript file that runs in the background, enabling offline support, push notifications, and background sync for web apps.

A small piece of data stored in the browser by a website to remember user preferences, login state, or tracking information.

SPA (Single Page Application)

A web application that loads a single HTML page and dynamically updates content without full page reloads.

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