Every few months someone benchmarks Bun doing something at 3x the speed of Node.js and Twitter goes feral. We've been through this cycle enough times now that we wanted to sit down and write something useful — not a benchmark flex, but an honest look at whether you should actually migrate your production app.
Short answer: probably not yet, but keep watching it. Here's the long answer.
What Bun Actually Is (And What It Isn't)
Bun isn't just a JavaScript runtime. It's a whole toolchain — runtime, package manager, bundler, test runner, all in one binary. That's either brilliant or terrifying depending on how many times you've been burned by 'all-in-one' tools in the past.
The runtime itself is built on JavaScriptCore (Safari's engine) instead of V8 (Chrome/Node's engine). This is a meaningful difference. JSC tends to start faster and use less memory. V8 tends to have a better JIT for long-running processes that warm up over time. If your workload is lots of short-lived processes or scripts — Bun wins pretty clearly. If you're running a long-lived server handling millions of requests over hours, the gap closes.
Bun is a runtime AND a package manager AND a bundler AND a test runner. That's a lot of surface area to trust with your production app.
The Benchmark Problem
Every Bun benchmark shows something like '3x faster HTTP throughput than Node.js'. And those numbers are real. But here's the thing: HTTP throughput in a microbenchmark is almost never your bottleneck in a real app.
Your app is slow because of database queries, third-party API calls, heavy JSON serialization, or bad caching decisions. The runtime itself handling HTTP is spending maybe 1-5% of the total request time. Making that 3x faster saves you... almost nothing.
What actually matters is how the runtime performs in your specific workload. Startup time matters if you're running serverless functions that cold-start constantly. Memory usage matters if you're on a $6/month VPS. Raw throughput matters if you're writing something like a proxy or an API gateway with no external dependencies.
- Startup time: Bun wins clearly — ~3-5x faster cold starts than Node.js
- Memory usage: Bun uses noticeably less RAM at idle
- Raw HTTP throughput: Bun wins in benchmarks, difference is smaller in real apps
- Long-running server performance: Comparable once V8 warms up
- Package install speed: Bun is dramatically faster than npm, and faster than pnpm
Where Bun Actually Shines Right Now
We've been using Bun as a package manager on several projects. Not as a runtime — just `bun install` instead of `npm install` or `pnpm install`. And honestly, this alone is worth it. On a project with 300+ dependencies, install time went from ~45 seconds with npm to ~8 seconds with Bun. That adds up when you're rebuilding Docker images or running CI.
# Use Bun just for package management in your existing Node.js project
# Install Bun
curl -fsSL https://bun.sh/install | bash
# Replace npm/pnpm installs
bun install
bun add some-package
bun remove old-package
# Your scripts still work the same
bun run dev
bun run build
bun run test
# But your runtime is still Node.js — no migration neededThe test runner is also genuinely good. It's Jest-compatible, runs fast, and the syntax is familiar. If you're starting a new project and don't have deep Jest config invested, `bun test` is worth trying.
// bun test is compatible with Jest syntax
import { describe, it, expect, beforeEach } from 'bun:test';
describe('UserService', () => {
let userService: UserService;
beforeEach(() => {
userService = new UserService();
});
it('should create a user with hashed password', async () => {
const user = await userService.create({
email: 'test@example.com',
password: 'plaintext123',
});
expect(user.email).toBe('test@example.com');
expect(user.password).not.toBe('plaintext123');
});
it('should throw when email already exists', async () => {
await userService.create({ email: 'dupe@example.com', password: 'pass' });
expect(
userService.create({ email: 'dupe@example.com', password: 'pass' })
).rejects.toThrow('Email already in use');
});
});The Compatibility Problem (The Honest Part)
Here's where we get real. Bun claims Node.js compatibility, and for most things it's pretty good. But 'pretty good' is different from 'perfect', and in production, you want perfect.
We hit a wall with some native addons. Anything that uses N-API or native bindings needs to be recompiled for Bun. Some packages just don't work. Not common packages — we're talking edge cases — but if you have a specific dependency that uses native modules, you might be blocked.
The bigger issue is the ecosystem around your runtime. Your deployment infrastructure (Dockerfile base images, AWS Lambda layers, etc.), your monitoring tools, your performance profilers — they're all built for Node.js. Bun has Bun-specific tooling but it's thinner. When something goes wrong at 2am (and it will), you want a well-worn path with Stack Overflow answers and GitHub issues. Bun's path is shorter.
- Some native addons don't work or need recompilation
- Fewer battle-tested deployment examples in the wild
- Some Node.js built-in APIs are partially implemented
- Bun's behavior on edge cases can differ from Node.js in subtle ways
- Your ops team probably knows Node.js, not Bun
What About Next.js Specifically?
This is probably what most of you actually care about. Can you run your Next.js app on Bun?
Yes, mostly. `bun run next dev` works. `bun run next build` works. The development experience is fine. The production runtime story is murkier — Next.js runs on Node.js, so even if you use Bun to start it, the actual Next.js server is still doing Node.js things internally. You're not getting the full Bun runtime benefits.
// package.json — using Bun to run scripts while Next.js still handles its own runtime
{
"scripts": {
"dev": "next dev",
"build": "next build",
"start": "next start",
"test": "bun test",
"lint": "next lint"
},
"engines": {
// Still target Node.js for deployment compatibility
"node": ">=18.0.0"
}
}Where Bun helps with Next.js: package installs, running local scripts, maybe your test suite. Where it doesn't magically speed things up: the actual server-side rendering, API routes, database queries — all the stuff that takes actual time.
If you're deploying to Vercel, you're on Node.js regardless. Vercel doesn't support Bun as a runtime (as of writing this). Same for most managed platforms. You'd need to self-host with Docker to actually run Bun as your production runtime, which is a meaningful infrastructure investment.
The Decision Framework
So how do you decide? We think about it like this:
Use Bun as your package manager today, no questions asked. The risk is near zero and you get real speed benefits on CI and local dev. If `bun install` breaks something (it's rare but possible with some lockfile edge cases), switching back to npm is one command.
Use Bun as your test runner if you're starting fresh or don't have heavy Jest customization. Again, low risk, real gain.
Use Bun as your runtime if: you're building something new with no legacy dependencies, you're comfortable self-hosting, your workload actually benefits from faster startup (lots of short-lived processes, scripts, CLIs), and you're willing to hit occasional rough edges and file issues.
Don't migrate an existing production Node.js app to Bun just because of benchmark posts. The risk/reward isn't there unless you have a specific pain point Bun solves.
// If you DO go full Bun runtime, here's a basic HTTP server
// This is genuinely faster than Node's http module
const server = Bun.serve({
port: 3000,
async fetch(request) {
const url = new URL(request.url);
if (url.pathname === '/health') {
return Response.json({ status: 'ok', runtime: 'bun' });
}
if (url.pathname === '/api/users' && request.method === 'GET') {
// Your actual logic here
const users = await db.query.users.findMany();
return Response.json(users);
}
return new Response('Not found', { status: 404 });
},
error(error) {
console.error(error);
return new Response('Internal server error', { status: 500 });
},
});
console.log(`Server running on http://localhost:${server.port}`);The Real Talk: Where We Think This Goes
We think Bun will be a serious contender in 2-3 years. The team is moving fast, the Node.js compatibility is improving with every release, and the toolchain story (one binary for everything) is genuinely appealing for developer experience.
The current state feels like Node.js circa 2012 — real potential, rough edges, not something you'd put your most critical production system on without a lot of testing. But the trajectory is good.
For our own work at peal.dev — building Next.js templates that people actually deploy to production — we're on Node.js with Bun as the package manager. Our templates use pnpm or npm in their documentation because that's what most developers are comfortable debugging. We might shift that default as Bun matures.
The best runtime is the one your team can debug at 2am without Googling 'why does Bun behave differently than Node here'.
Watch the Bun changelog. Try it on a side project. Use it as your package manager right now. But don't rewrite your infrastructure because someone's HTTP benchmark looked impressive on Twitter. That's the kind of decision that looks exciting on a Thursday and looks like a massive mistake the following Monday when something breaks in prod.
When in doubt, the boring choice keeps your app up. And an app that's up beats one that's theoretically faster but needs babysitting.