How do I build a GraphQL API?

Building a GraphQL API usually looks like this:

1) Define your schema

Your schema is the contract for what clients can ask for.

Example:

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

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

This says:

• user(id:) returns one user
• users returns a list of users
• each User has id, name, and email

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2) Pick a server library/framework

Common choices:

• JavaScript/TypeScript: Apollo Server, GraphQL Yoga, Mercurius
• Python: Strawberry, Ariadne, Graphene
• Java: Spring for GraphQL, graphql-java
• Go: gqlgen
• Ruby: graphql-ruby

If you want the easiest start in JS/TS, Apollo Server is popular.

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3) Write resolvers

Resolvers are the functions that fetch the actual data.

Example in JavaScript:

const resolvers = {
  Query: {
    user: (_, { id }) => ({ id, name: "Alice", email: "alice@example.com" }),
    users: () => [
      { id: "1", name: "Alice", email: "alice@example.com" },
      { id: "2", name: "Bob", email: "bob@example.com" },
    ],
  },
};

• The schema defines what exists
• Resolvers define how to get it

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4) Connect to a data source

Usually you’ll fetch from:

• a database
• REST APIs
• another service
• in-memory data for testing

Example with a database:

• resolver calls a service
• service queries PostgreSQL/MongoDB/etc.

---

5) Add a GraphQL server

Example using Apollo Server:

import { ApolloServer } from '@apollo/server';
import { startStandaloneServer } from '@apollo/server/standalone';

const typeDefs = `#graphql
  type Query {
    user(id: ID!): User
    users: [User!]!
  }

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

const resolvers = {
  Query: {
    user: (_, { id }) => ({ id, name: "Alice", email: "alice@example.com" }),
    users: () => [
      { id: "1", name: "Alice", email: "alice@example.com" },
      { id: "2", name: "Bob", email: "bob@example.com" },
    ],
  },
};

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

const { url } = await startStandaloneServer(server, {
  listen: { port: 4000 },
});

console.log(`Server ready at ${url}`);

---

6) Test with a query

You can query it like this:

query {
  users {
    id
    name
  }
}

Response:

{
  "data": {
    "users": [
      { "id": "1", "name": "Alice" },
      { "id": "2", "name": "Bob" }
    ]
  }
}

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7) Add common production features

You’ll usually want:

• Authentication/authorization
• Validation
• Error handling
• Pagination
• Caching
• Rate limiting
• Logging/monitoring
• Database batching to avoid N+1 queries
• Schema versioning strategy via deprecation instead of breaking changes

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8) Expose mutations for writes

For changing data:

type Mutation {
  createUser(name: String!, email: String!): User!
}

Resolver example:

Mutation: {
  createUser: (_, { name, email }) => {
    return { id: "3", name, email };
  },
}

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9) Consider subscriptions if you need real-time updates

For example:

• chat messages
• live notifications
• streaming updates

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10) Best practices

• Keep the schema focused and user-friendly
• Use DataLoader or batching to avoid N+1 issues
• Prefer pagination for lists
• Make fields nullable only when needed
• Avoid exposing your database structure directly
• Use input types for mutations

Example:

input CreateUserInput {
  name: String!
  email: String!
}

type Mutation {
  createUser(input: CreateUserInput!): User!
}

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Suggested learning path

1. Learn the basics of GraphQL queries, mutations, and schema
2. Build a small API with mock data
3. Add a real database
4. Add auth and pagination
5. Add subscriptions if needed
6. Deploy

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If you want, I can also give you:

• a complete GraphQL API example in Node.js
• a Python/FastAPI GraphQL example
• or a step-by-step tutorial with a database