What is GraphQL?

What is GraphQL?

GraphQL is a query language for APIs and a runtime for executing those queries against your data. It was developed internally by Facebook in 2012 and open-sourced in 2015. Unlike REST, where the server decides what data to send, GraphQL lets the client specify exactly what data it needs.

The Problem with REST

In a traditional REST API, you have multiple endpoints:

GET /api/users/123
GET /api/users/123/posts
GET /api/users/123/followers

This leads to two major issues:

• Over-fetching — You get more data than you need. For example, fetching a user might return 20 fields when you only need the name and avatar.
• Under-fetching — You don't get enough data in a single request, forcing multiple round-trips to the server.

How GraphQL Solves This

With GraphQL, there is typically one single endpoint (e.g., /graphql), and the client sends a query describing exactly what it wants:

{
  user(id: "123") {
    name
    avatar
    posts {
      title
    }
  }
}

The server responds with exactly that shape of data — nothing more, nothing less:

{
  "data": {
    "user": {
      "name": "John Doe",
      "avatar": "https://example.com/avatar.jpg",
      "posts": [
        { "title": "My First Post" },
        { "title": "Learning GraphQL" }
      ]
    }
  }
}

Key Benefits of GraphQL

• Precise data fetching — ask for exactly what you need
• Single endpoint — no more managing dozens of REST endpoints
• Strongly typed schema — the API is self-documenting
• Real-time updates — built-in subscription support
• Great developer tools — tools like GraphiQL and Apollo DevTools

GraphQL vs REST — Quick Comparison

Feature	REST	GraphQL
Endpoints	Multiple (/users, /posts)	Single (/graphql)
Data fetching	Server decides	Client decides
Over-fetching	Common	Eliminated
Type system	Optional (OpenAPI)	Built-in
Learning curve	Low	Moderate

When to Use GraphQL

GraphQL is ideal when:

• Your app has complex, nested data relationships
• You serve multiple clients (web, mobile, IoT) with different data needs
• You want to reduce the number of network requests
• You need a strongly-typed, self-documenting API

Key Takeaways

• GraphQL is a query language for APIs, not a database
• It solves over-fetching and under-fetching problems of REST
• The client describes the shape of the response
• It uses a single endpoint with a strongly-typed schema

In the next episode, we'll dive into Query Basics and learn the syntax for writing GraphQL queries.