REST vs GraphQL: When to use which? | API Interview Questions

What You'll Learn

Key differences
Pros and cons
When to choose each

Comparison

Feature	REST	GraphQL
Endpoints	Multiple	Single
Data fetching	Server decides	Client decides
Over-fetching	Common	Avoided
Caching	Easy (HTTP cache)	Complex
Learning curve	Lower	Higher
File uploads	Simple	More complex

REST Example

code.jsJavaScript

// Need 3 requests for user, posts, and comments
GET /users/1
GET /users/1/posts
GET /posts/1/comments

// May get more data than needed
{
  "id": 1,
  "name": "John",
  "email": "...",
  "address": "...",  // Not needed
  "phone": "...",    // Not needed
}

GraphQL Example

code.txtGRAPHQL

# Single request, exact data needed
query {
  user(id: 1) {
    name
    posts {
      title
      comments {
        text
      }
    }
  }
}

When to Use REST

Simple CRUD operations
Public APIs with caching needs
File uploads/downloads
Team new to GraphQL
Microservices communication

When to Use GraphQL

Complex data requirements
Mobile apps (bandwidth sensitive)
Rapidly evolving frontend needs
Multiple client types
Nested/related data queries