I Benchmarked Bun vs Node.js vs Deno So You Don't Have To

I spent way too much time running these stupid benchmarks, but here's what you actually need to know about JavaScript runtime performance.

The HTTP Server Test That Made Me Question Everything

I threw together some Hello World servers to see if the performance claims were complete bullshit. Nothing fancy - just wanted to see what all the hype was about.

Node.js with Express: Started choking around 12-14K requests per second
Bun with native server: Hit like 50K+ req/s and kept going
Deno: Managed around 15-17K req/s

That's a massive difference, and I saw it consistently across multiple runs on my M2 MacBook with 16GB RAM. Your numbers will definitely be different depending on your hardware and network setup. Bun really is that much faster for HTTP - check TechEmpower benchmarks if you don't believe me.

But here's the thing: this only matters if you're actually serving tons of HTTP requests. Most apps spend their time waiting for database queries, not pumping out responses. That speed advantage disappears when your Postgres query takes 50ms.

CPU Tasks: Where JavaScriptCore Actually Shines

I threw together a stupid CPU test that sorts a bunch of random numbers - you know, the kind of thing that makes your laptop fan spin up.

Node.js: Took about 3.4 seconds
Bun: Finished in roughly half that time
Deno: Somewhere in between

JavaScriptCore (which Bun uses) starts fast and stays fast. V8 needs time to warm up but can be faster for long-running stuff. That's why Bun feels snappier for CLI tools and build scripts - things that run once and exit. Safari's engine optimization focuses on fast startup, while Chrome's approach prioritizes peak performance.

Memory Usage Reality Check

Bun seems to use less memory - maybe 20-30% less based on what I saw in htop, but I didn't do rigorous testing. Deno sits somewhere in the middle.

In practice, this means Bun might run better on cheap VPS instances, but unless you're really memory-constrained, it's not a huge deal. Memory optimization matters more for containerized deployments where you pay per MB.

The One Thing That Actually Changed My Daily Workflow

Package installation with Bun is stupidly fast. I'm talking npm takes 2+ minutes, Bun takes like 8 seconds for the same dependencies. It's written in Zig and optimized for speed, using modern package resolution algorithms.

This actually matters because waiting for npm install is soul-crushing. My CI builds that used to take 5 minutes now finish in under 2 minutes with proper caching strategies.

TypeScript execution - both Bun and Deno just run .ts files. No `ts-node` bullshit, no build steps. You run bun server.ts and it works. This alone makes development way less annoying than Node.js's complex TypeScript setup.

The Gotchas That Will Waste Your Afternoon

Bun breaks random shit - some SQLite compatibility issue didn't work and I wasted 3 hours before finding a buried GitHub issue about it. Most popular npm packages work fine, but when something breaks, you're basically on your own without Stack Overflow answers.

Deno's permission system will confuse you at first. You'll get `PermissionDenied: access to "."` errors and spend 20 minutes figuring out you need --allow-read=. or whatever. It's actually useful once you get used to it, but the initial learning curve sucks.

Node.js is boring and that's exactly what you want at 3am when something breaks in production. Everyone knows how to debug it, Stack Overflow has answers, and it just works.

Should You Actually Switch? (Probably Not)

After three weeks of testing, here's my honest take on when to use each runtime.

Stick With Node.js If You're Smart

Don't migrate existing production apps.

I don't care how much faster Bun is

• migrating a working production system for performance gains is engineering masturbation unless you have a specific performance problem that Node.js can't solve.

Large teams should stick with Node.js because everyone knows how to debug it.

When your app breaks at 3am, you want the on-call engineer to know exactly where to look. The debugging ecosystem is mature and battle-tested.

Enterprise environments

• if you work at a bank or insurance company, just use Node.js.

The LTS support is active until October 2025, then maintenance until April 2027.

Risk-averse organizations need that predictability.

Windows development teams should probably stick with Node.js. While Bun technically supports Windows now, the tooling integration isn't as smooth. VS Code debugging, PowerShell scripts, and corporate VPN compatibility just work better with Node.js.

Use Bun for New Projects (Maybe)

New TypeScript APIs

• this is where Bun really shines.

No more fucking around with `ts-node` or build steps.

Just run bun server.ts and it works. I converted a TypeScript Express API to Bun and the development experience is legitimately better.

Developer tooling and CLI apps

• if you're building scripts, build tools, or anything that runs once and exits, Bun's speed advantage is noticeable. Package installation is like 10× faster, Type

Script execution is instant, and the built-in bundler eliminates tool complexity.

High-throughput APIs

• if you're building something that needs to handle thousands of concurrent connections (API gateways, websocket servers, real-time apps), the 3-4x HTTP performance advantage translates to real infrastructure cost savings.

Serverless functions

• the ~50-80ms cold start vs Node's like 150-200ms matters when users are waiting. AWS Lambda charges by execution time, so faster startup literally saves money. Vercel Edge Functions also benefit from faster cold starts.

Deno 2.0 is Finally Worth Considering

Deno 2.0 dropped in October 2024 and it's actually decent now.

Better npm compatibility, improved performance, and the security stuff is less annoying.

Security-conscious applications

• Deno's permission system is actually useful if you're handling sensitive data. Instead of trusting every npm package with full system access, you explicitly grant permissions.

It's confusing at first but makes sense once you get it.

Modern web development

• Deno implements web standards correctly. Fetch API, Web Crypto, and Web Workers work exactly like in browsers.

No more `node-fetch` or polyfills.

Cross-platform library development

• JSR packages work in Node.js, Deno, and Bun without separate builds.

If you're publishing libraries, this is genuinely useful.

Migration Reality Check

Start with CLI tools and new services

• don't migrate your main application. Build new microservices with Bun or Deno to gain experience without risking production stability.

Test your dependencies

• that obscure npm package you depend on might not work with Bun.

I wasted 2 hours on a SQLite issue that turned out to be a Bun compatibility problem buried in GitHub issues.

Budget time for learning curves

• Deno's permission system takes a week to figure out. Bun's ecosystem gaps will surprise you.

Node.js just works because everyone's already solved the problems.

My Honest Recommendations

For most teams:

Stick with Node.js for production, mess around with Bun for CLI tools and development stuff.

For new teams: Maybe try Deno 2.0 if you want modern web standards and don't have a bunch of legacy crap to deal with.

For performance-critical stuff: Bun might be worth it if HTTP throughput is actually your bottleneck, not your database queries.

The performance differences are real, but most apps are limited by database queries and external API calls rather than JavaScript runtime speed. Don't choose based on benchmark porn

• pick what works for your actual constraints.