What Is GraphQL?

GraphQL is a query language for APIs. Clients request exactly the data they need. Solves over-fetching and under-fetching problems.

REST Approach

// Multiple endpoints needed
GET /users/1
GET /users/1/posts
GET /users/1/followers

// Often returns too much or too little data

GraphQL Approach

query {
  user(id: 1) {
    name
    posts { title }
    followers { name }
  }
}

// One request, exact data needed

Apollo Server Setup

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

const typeDefs = gql`
  type User {
    id: ID!
    name: String!
    email: String!
  }
  type Query {
    users: [User]
    user(id: ID!): User
  }
`;

const resolvers = {
  Query: {
    users: () => db.getUsers(),
    user: (_, { id }) => db.getUser(id)
  }
};

Conclusion

Use REST for simple APIs and easy caching. Choose GraphQL for complex, interconnected data and mobile apps.