​​​​​​​What is GraphQL?

GraphQL is a query language for APIs and a runtime for executing those queries based on your data.
It was developed by Facebook and released publicly in 2015.

Unlike REST, where you access multiple endpoints to get data, GraphQL allows you to request exactly the data you need with a single query.

🚀 Why Use GraphQL?

Feature	Benefit
Single Endpoint	All queries go to one `/graphql` endpoint (no need for many URLs)
Exact Data Fetching	You get only the fields you request (no overfetching)
Nested Requests	Easily fetch related data (like user → posts → comments)
Strong Typing	GraphQL uses a schema that defines types and their relationships
No Versioning Needed	Schema evolves, so APIs don't need `v1`, `v2`, etc.
Real-time Support	With subscriptions, GraphQL can deliver live updates

📄 How Does GraphQL Work?

1. Client sends a query:

query {
  user(id: "1") {
    name
    email
    posts {
      title
      likes
    }
  }
}

This asks for:

A user with id = 1
Their name and email
A list of their posts with title and likes

2. Server responds with exactly the data requested:

{
  "data": {
    "user": {
      "name": "Alice",
      "email": "[email protected]",
      "posts": [
        {
          "title": "GraphQL 101",
          "likes": 120
        },
        {
          "title": "Advanced Queries",
          "likes": 75
        }
      ]
    }
  }
}

🧱 GraphQL Schema Basics

A schema defines the structure of your API.

Example:

type User {
  id: ID!
  name: String!
  email: String!
  posts: [Post]
}

type Post {
  id: ID!
  title: String!
  likes: Int
}

type Query {
  user(id: ID!): User
}

type User: A user object with fields
Query: Defines available read operations
!: Means the field is required

🔧 Common Use Cases

Mobile apps: Limit bandwidth by fetching only necessary fields
Microservices: Combine data from multiple services into one API
Modern web apps: Faster UI rendering with exact data

🛠 Popular Tools and Libraries

Tool	Purpose
Apollo	Client & server GraphQL toolkit
Relay	GraphQL framework by Facebook
GraphiQL	In-browser IDE for testing queries
Hasura	Instant GraphQL on your database

💡 GraphQL vs REST Summary

GraphQL	REST
One endpoint	Multiple endpoints
Get exactly what you need	Fixed response structure
No versioning	Versioning often needed
Strong schema	Often lacks type definitions

🔚 Summary

GraphQL = Modern, Flexible, Efficient API Design.
It lets you build powerful applications faster by giving clients control over the data they need — and avoiding under- or over-fetching.