GraphQL

Query Language for APIs

GraphQL lets clients request exactly the data they need, solving over-fetching and under-fetching problems common with REST.

Core Concepts

• Schema: Type definitions describing your data
• Queries: Read operations
• Mutations: Write operations
• Resolvers: Functions that fetch data for each field
• Subscriptions: Real-time updates via WebSocket

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

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

# Query Example
query {
  user(id: "1") {
    name
    posts {
      title
    }
  }
}

Benefits

• Single endpoint for all data needs
• Strongly typed schema
• Built-in documentation (introspection)
• Efficient data loading with DataLoader

Considerations

• N+1 query problem (solved by DataLoader)
• Caching is more complex than REST
• Query complexity and depth limiting