What is GraphQL?

◕ GraphQLLesson 1Beginner

GraphQL is a query language for APIs and a runtime for executing those queries, developed by Facebook in 2012 and open-sourced in 2015. Unlike REST, GraphQL lets clients request exactly the data they need — no more, no less — in a single request.

1 The Core Problems GraphQL Solves

Over-fetching: REST returns entire objects even when you only need two fields. GraphQL returns only what you ask for.
Under-fetching: REST often requires multiple round-trips (e.g., fetch user, then fetch their posts, then fetch post comments). GraphQL fetches it all in one query.
Rigid endpoints: REST has fixed URL endpoints. GraphQL exposes a single endpoint (/graphql) and the query shape determines the response.
Type safety: GraphQL schemas are strongly typed, enabling tooling, auto-complete, and validation at the schema level.

2 REST vs GraphQL Side-by-Side

REST — Multiple Requests

GET /users/1        -> { id, name, email, address, phone, ... } (over-fetch)
GET /users/1/posts  -> [ { id, title, body, createdAt, ... } ]
GET /posts/42/comments -> [ { id, text, author, ... } ]

// 3 round trips, lots of unused data

GraphQL — Single Request, Exact Data

POST /graphql

# Query
{
  user(id: "1") {
    name
    posts {
      title
      comments {
        text
        author { name }
      }
    }
  }
}

# Response — exactly what was asked
{
  "data": {
    "user": {
      "name": "Balaji",
      "posts": [{ "title": "...", "comments": [...] }]
    }
  }
}

3 When to Use GraphQL vs REST

Scenario	Best Choice
Public API with many different consumers	REST
Complex UIs with many data relationships	GraphQL
Mobile apps (limited bandwidth)	GraphQL
Simple CRUD microservices	REST
Real-time features	GraphQL (Subscriptions)
Third-party integrations	REST

4 Code Challenge

Challenge: Explore the public GitHub GraphQL API at https://api.github.com/graphql using the GitHub Explorer. Write a query that fetches your GitHub username, your 5 most recent repositories (name + star count), and your follower count — all in one request.