Introduction to GraphQL

GraphQL is a query language for APIs and a runtime for executing those queries by providing a type system for your data. It allows clients to request exactly the data they need, making it more efficient than traditional REST APIs.

Unlike REST, where you have multiple endpoints, GraphQL has a single endpoint. Clients can fetch multiple resources in a single request.

1. Queries

Queries are used to request data. Here's a simple example:

{
  user(id: "1") {
    name
    email
  }
}
                

2. Mutations

Mutations are used to modify server-side data. Example:

mutation {
  createUser(input: { name: "John", email: "john@example.com" }) {
    id
    name
  }
}
                

3. Subscriptions

Subscriptions allow clients to listen to real-time updates. Example:

subscription {
  userUpdated {
    id
    name
  }
}
                

To set up a GraphQL server, you can use libraries like Apollo Server or express-graphql.

Example using Apollo Server:

const { ApolloServer, gql } = require('apollo-server');

// Define your schema
const typeDefs = gql`
  type User {
    id: ID!
    name: String!
    email: String!
  }

  type Query {
    users: [User]
  }
`;

// Provide resolver functions for your schema
const resolvers = {
  Query: {
    users: () => [{ id: "1", name: "John", email: "john@example.com" }],
  },
};

const server = new ApolloServer({ typeDefs, resolvers });

server.listen().then(({ url }) => {
  console.log(`🚀  Server ready at ${url}`);
});
                

• Always validate queries to prevent malicious requests.
• Use pagination for large data sets.
• Implement caching strategies for better performance.