Migration from REST to GraphQL

Introduction

Moving from REST to GraphQL helps you get exactly the data you want in one request. It makes your app faster and easier to build.

You want to reduce multiple REST calls into a single request.

You need flexible queries that return only the data you need.

Your app has complex data relationships that REST handles inefficiently.

You want to improve frontend and backend communication.

You want to avoid over-fetching or under-fetching data.

Syntax

GraphQL

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

type User {
  id: ID!
  name: String
  email: String
}

GraphQL uses a single endpoint for all queries instead of multiple REST endpoints.

You define types and queries that describe exactly what data can be requested.

Examples

REST uses a URL to get user data. GraphQL uses a query to ask for specific fields.

GraphQL

# REST example
GET /users/1

# GraphQL equivalent
{
  getUser(id: "1") {
    id
    name
    email
  }
}

GraphQL fetches user and posts in one request, unlike REST which needs two calls.

GraphQL

# REST multiple calls
GET /users/1
GET /users/1/posts

# GraphQL single call
{
  getUser(id: "1") {
    id
    name
    posts {
      id
      title
    }
  }
}

You can ask for just the user's name, avoiding extra data.

GraphQL

# Request only needed fields
{
  getUser(id: "1") {
    name
  }
}

Sample Program

This schema defines a user and their posts. The query asks for user details and their posts in one request.

GraphQL

# GraphQL schema definition
schema {
  query: Query
}

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

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

type Post {
  id: ID!
  title: String
}

# Sample query
{
  getUser(id: "1") {
    id
    name
    email
    posts {
      id
      title
    }
  }
}

Important Notes

GraphQL reduces the number of requests by combining data fetching.

It requires defining a schema that describes your data and queries.

Common mistake: Trying to replicate REST endpoints exactly instead of designing flexible queries.

Summary

GraphQL lets you ask for exactly what you need in one request.

It improves efficiency by reducing over-fetching and under-fetching.

Migration means defining a schema and rewriting client queries.