Bun App Architecture

🏗️ Bun App Architecture — Designing Scalable & Performant Apps

As Bun rapidly gains traction as a high-speed JavaScript runtime, developers are seeking effective architectural patterns to build solid, scalable apps with it. In this blog, we’ll explore how to structure your Bun applications for maintainability, modularity, and performance. Whether you're crafting APIs, microservices, or full-stack platforms — having a clean architecture is 🔑!

📦 Understanding Bun's Philosophy

Bun is built in Zig and provides an all-in-one runtime, bundler, transpiler, and package manager. This unification simplifies setup and accelerates performance. Unlike Node.js, you don’t need external tools like Babel, Webpack, or even npm.

• ⚡ Extremely fast module resolution
• 📦 Native bundling and transpiling
• 🔥 Built-in support for JSX, TypeScript, and ESModules

🧱 Layered Architecture Overview

A clean Bun app structure typically follows a layered approach:

bun-app/
│
├── src/
│   ├── config/
│   ├── controllers/
│   ├── services/
│   ├── routes/
│   ├── models/
│   ├── utils/
│   └── index.ts
│
├── public/
├── .env
└── bunfig.toml

Each folder serves a purpose:

• config: Environment and setup files
• controllers: Handle incoming HTTP requests
• services: Business logic layer
• routes: API endpoint definitions
• models: Database schema and ORMs
• utils: Reusable helper functions

🌐 Creating a Simple Server

src/index.ts

const server = Bun.serve({
  port: 3000,
  fetch(req) {
    return new Response("Welcome to your Bun App! 🚀");
  },
});

console.log(`Listening on http://localhost:${server.port}`);

🛣️ Routing with Controllers

src/routes/userRoutes.ts

import { getAllUsers } from "../controllers/userController";

export const routes = [
  {
    path: "/users",
    method: "GET",
    handler: getAllUsers
  }
];

src/controllers/userController.ts

export async function getAllUsers(req: Request): Promise {
  const users = [
    { name: "Alice", age: 30 },
    { name: "Bob", age: 25 }
  ];
  return new Response(JSON.stringify(users), {
    headers: { "Content-Type": "application/json" }
  });
}

🧠 Service Layer for Logic

src/services/userService.ts

export function fetchUsersFromDB() {
  // Simulated DB logic
  return [{ id: 1, name: "Simulated User" }];
}

⚙️ Environment Config

Set environment variables in a .env file and load them using:

import "dotenv/config";
const API_KEY = process.env.API_KEY;

📁 Modularizing with Utilities

src/utils/logger.ts

export function logInfo(message: string) {
  console.log(`[INFO]: ${message}`);
}

🧪 Suggested Improvements

To scale your Bun app further, consider integrating:

• 🧵 Worker threads for async processing
• 🧩 Middleware pattern for auth/logging
• 🧪 Unit testing with libraries like uvu or jest

🚀 Final Thoughts

While Bun is still evolving, its potential for speed and simplicity is massive. A well-structured Bun app architecture ensures your project stays maintainable and scalable as it grows. Stick to modular principles, keep concerns separated, and use Bun's native capabilities to their fullest. 🎯

Start simple, scale smart. Happy hacking with Bun! 💡🔥