The Complete Guide to GraphQL

GraphQL is an alternative to REST. Clients request exactly the data they need.

REST vs GraphQL¶

• REST: multiple endpoints, fixed responses
• GraphQL: single endpoint, flexible queries
• REST: over/under-fetching
• GraphQL: exactly what you need

Schema¶

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

type Post {  
  id: ID!  
  title: String!  
  author: User!  
}

Query¶

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

Mutation¶

mutation {  
  createUser(input: { name: "John", email: "[email protected]" }) {  
    id  
    name  
  }  
}

Subscription (real-time)¶

subscription {  
  messageAdded(channelId: "general") {  
    id  
    text  
    author { name }  
  }  
}

N+1 Problem¶

GraphQL resolver for posts can trigger N database queries. Solution: DataLoader for batching.

When to Use GraphQL¶

• Mobile apps (minimize network traffic)
• Complex nested data
• Multiple clients with different needs
• Real-time with subscriptions

When NOT to Use¶

• Simple CRUD API
• File uploads (REST is simpler)
• Caching (REST + CDN is simpler)

Recommendations¶

REST is sufficient for most APIs. Add GraphQL when you have complex data requirements or multiple clients.