Bun.js for GraphQL APIs

🚀 Introduction to Bun.js for GraphQL APIs

GraphQL is a modern API query language that gives clients the power to request only what they need. When combined with Bun.js—the ultra-fast JavaScript runtime—you get a high-performance backend environment with a minimal footprint. This blog shows how to build GraphQL APIs using Bun.js with practical examples.

🔧 Setting Up the Project

Before jumping into code, let’s create a fresh Bun project and install necessary packages:

bun init graphql-api
cd graphql-api
bun add graphql graphql-yoga

We’re using graphql for core GraphQL utilities and graphql-yoga to quickly spin up a GraphQL server, all compatible with Bun.

📦 Creating a Simple GraphQL Schema

Let’s define a simple schema with a query to fetch user data.

// schema.js
import { createSchema } from "graphql-yoga";

export const schema = createSchema({
  typeDefs: /* GraphQL */ `
    type User {
      id: ID!
      name: String!
      email: String!
    }

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

This schema exposes a users query that returns a static list of user objects.

🖥️ Creating the GraphQL Server

Now, let’s set up the HTTP server using Bun.js and wire up our schema.

// server.js
import { createServer } from "node:http";
import { createYoga } from "graphql-yoga";
import { schema } from "./schema";

const yoga = createYoga({ schema });

const server = createServer(yoga);

server.listen(4000, () => {
  console.log("🚀 GraphQL Server running on http://localhost:4000/graphql");
});

Simply run this using:

bun server.js

You now have a fully functional GraphQL server running on Bun at /graphql!

📬 Testing Your GraphQL API

Navigate to http://localhost:4000/graphql and enter this query in the GraphiQL interface:

{
  users {
    id
    name
    email
  }
}

You should receive the mock users defined in your resolver.

🧩 Adding Dynamic Data and Parameters

Let’s enhance our API to accept parameters and simulate a database call:

// Update schema.js
type Query {
  user(id: ID!): User
}

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

You can now query individual users with:

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

📈 Why Use Bun.js for GraphQL?

• Lightning-fast performance: Bun.js uses JavaScriptCore, which is highly optimized
• Built-in TypeScript support: No config needed
• Easy dependency management with bun install
• Zero bloat: Keep your API minimal and efficient

⚙️ Tips for Production-Ready APIs

• Use environment variables for secrets
• Add validation in your resolvers
• Implement error handling for failed queries
• Use a database like PostgreSQL or MongoDB via external drivers

✅ Conclusion

GraphQL and Bun.js are a match made for speed, simplicity, and control. With just a few lines of code, you can create powerful, modern APIs that scale. Whether you’re building a monolith or microservices, using Bun for GraphQL APIs keeps things fast, lean, and elegant. Try expanding your schema, connect to a real DB, and start building blazing-fast backends today!