Bun vs Deno vs Node.js: Which Runtime Won't Ruin Your Weekend

Runtime benchmarks are mostly bullshit. I learned this when my Bun migration crashed every 20 minutes with SIGSEGV errors.

Bun is genuinely faster - my Express API went from 8k RPS to 24k RPS on the same hardware. But speed means nothing when your process randomly dies with no useful error message. Bun 1.2.0 fixed most stability issues, but you're still beta testing for them. The JavaScriptCore engine has better memory performance than V8 in many cases - when it doesn't segfault.

Deno 2.0 is the adult in the room now - stable, predictable, and only 20% slower than Node.js in real-world HTTP workloads. The TypeScript support is legitimately amazing: no build step, no config files, just works. But good luck explaining the permission system to your DevOps team.

Node.js 22 just works - boring, reliable, and every monitoring tool knows how to profile it. It's the runtime equivalent of a Toyota Camry: not exciting, but it starts every morning. The V8 engine optimizations continue improving performance steadily.

Bun consistently outperforms Node.js by 3x in HTTP benchmarks, but these numbers mean nothing when your app crashes due to compatibility issues. I spent my entire Saturday debugging this shit.

Why JavaScriptCore Will Ruin Your Weekend

Bun's JavaScriptCore engine sounds great on paper - better memory usage, faster cold starts. In practice, you'll spend hours debugging weird edge cases because 99% of JavaScript was written for V8.

I hit this with the `crypto` module: Node.js code that worked fine for 2 years suddenly started throwing ERR_CRYPTO_INVALID_STATE errors in Bun 1.1.8. The fix? Completely rewrite the crypto logic because JavaScriptCore handles buffer initialization differently than V8. Took me 6 hours and a lot of swearing. Check Bun's compatibility issues - you'll find way more pain than I signed up for.

V8 has 15 years of weird edge cases that every npm package was built around. V8's quirks are documented in millions of Stack Overflow posts. JavaScriptCore is technically cleaner but breaks shit that worked fine for years. The WebKit team optimizes for Safari, not server workloads where you need to run for months without crashes.

Deno's built-in TypeScript compiler eliminates the build step entirely - you write .ts files and Deno executes them directly. No webpack, no tsc, no config files.

TypeScript: The Good, Bad, and Ugly

Bun just runs .ts files without transpilation, which feels like black magic until you need to debug type errors and realize there's no source maps. Made me want to chuck my laptop out the window.

Deno's TypeScript is perfect when it works. The type checker is strict as hell, which means every slightly loose npm package throws 200 type errors. You'll either love it or develop an eye twitch.

Node.js with TypeScript is predictable pain. Everyone knows how to set up tsc, everyone's debugger works, and Stack Overflow has answers for everything.

Deno Security is Annoying as Hell

Deno's permission system is brilliant in theory. In practice, you'll type --allow-all and defeat the entire security model because debugging which permission you need is a nightmare.

## What you want to type:
deno run app.ts

## What you actually type after 30 minutes:
deno run --allow-all --allow-read --allow-write --allow-net --allow-env --allow-run app.ts

Node.js and Bun give your app full system access, which is terrifying but honest. At least you know what you're getting.

The real performance battle is between shipping features and fighting runtime quirks. Speed is meaningless if you're debugging crashes at 3am.

Node.js: The Devil You Know

Node.js has every package you'll ever need - and 50 that do the same thing but slightly differently. The npm ecosystem is a blessing and a curse. Need to parse CSV? There's 47 packages for that, and half of them haven't been updated since 2018. The npm audit will give you nightmares about security vulnerabilities.

But here's the thing: Node.js just fucking works. I've been running Node.js APIs in production for 8 years, and the worst problem I've had is a memory leak that took 3 months to surface. The tooling is mature, the debugging is predictable, and every DevOps engineer knows how to deploy it.

Node.js 22 is rock solid - the V8 engine is battle-tested on billions of Chrome instances. When something breaks, Google's army of engineers fixes it. The LTS releases mean you can deploy with confidence and get security patches for years. The Node.js Security Working Group actually takes security seriously.

The pain points? Memory usage is terrible (easily 200MB for a simple API), startup time sucks (3-5 seconds for large apps), and dependency management is still a clusterfuck even with package-lock.json. The node_modules directory will consume your entire SSD given enough time.

Bun: Fast and Dangerous

Bun 1.2 is legitimately impressive - it runs most of my Node.js code 3x faster with zero changes. The package manager is so fast it feels broken. Installing 500 packages takes 12 seconds instead of 2 minutes. The built-in bundler and test runner are actually useful tools.

The problems start when you hit edge cases. Native modules break randomly - I spent 6 hours debugging why `sharp` (image processing) would segfault with SIGSEGV every time I tried to resize a PNG in Bun but worked perfectly in Node.js 18. Turns out it's a known issue with native addon compilation. The GitHub issues are full of "works in Node.js, crashes in Bun" reports. Check the compatibility table before migrating anything important.

Bun's built-in libraries are actually useful - the HTTP client, SQLite driver, and file system utilities are faster than their npm equivalents. But you're trading ecosystem maturity for performance. Good luck debugging when something breaks at 3am.

The real killer: error messages are useless. Node.js gives you stack traces that make sense. Bun gives you JavaScriptCore engine crashes that look like someone sneezed assembly code onto your terminal.

Deno: Perfectionist's Paradise (Or Hell)

Deno 2.0 is what Node.js should have been - secure by default, TypeScript native, no node_modules hell. The standard library is well-designed, and the permission system actually prevents stupid security mistakes.

The downside? Everything is slightly harder. Want to use an npm package? You need to understand import maps. Want to read environment variables? You need --allow-env. Want to make HTTP requests? --allow-net. It's secure, but exhausting.

Deno Deploy is genuinely good - zero-config deployments that actually work. But the vendor lock-in is real. Good luck migrating to another platform when you've built your app around Deno KV and Deno Cron.

The community is small but enthusiastic. Stack Overflow has 10,000 Node.js answers and 100 Deno answers. When you hit a weird bug, you're probably the first person to hit it.

Package Management Hell

Bun's package manager is like cocaine - once you try it, npm feels like dial-up internet. But it's also buggy as shit. I've had it corrupt lockfiles, install wrong versions, and randomly forget about cached packages.

Deno's URL imports are elegant in theory - no package.json, no node_modules, just import from URLs. In practice, you'll spend hours figuring out why your dependencies aren't resolving correctly offline.

npm is terrible but predictable - slow, verbose, with dependency hell that occasionally ruins your day. But everyone knows how to fix npm problems. There's 15 years of Stack Overflow answers for every weird npm edge case.

Docker Reality Check

Bun containers are tiny - 80MB vs Node.js's 300MB. But good luck debugging inside the container when something breaks. The error messages are still garbage, and you can't attach a debugger easily.

Deno containers are clean - single binary, no dependencies, no bullshit. The production builds are actually reproducible, which is more than I can say for most Node.js apps.

Node.js containers are bloated but battle-tested. Every monitoring tool, every APM solution, every security scanner knows how to work with Node.js containers.

Good Luck Hiring Anyone Who Knows This Stuff

Want to hire Node.js developers? There's millions of them. Want to hire Bun experts? Good luck finding 10 people who've actually used it in production.

Deno developers are rare but tend to be very good - it attracts people who care about code quality and security. The downside is you'll pay 20% more and have a smaller candidate pool.

Migrating runtimes isn't just a technical decision - it's a business risk that affects your entire development workflow. And when shit breaks at 3am, you're the one getting called.