Which JavaScript Runtime Won't Make You Hate Your Life

I've deployed all three of these bastards in production. Node.js back in 2007 when it was held together with duct tape, Deno since 1.0 when everyone was convinced it would murder Node, and Bun since 1.0 dropped in September 2023. Here's what breaks when you're trying to debug at 3AM.

Visual guide to JavaScript event loop mechanics across different runtimes

Node.js: The Boring Choice That Works

Node.js is boring as shit and that's exactly why it works. We're running Node.js 22.x LTS in production, and honestly the worst part is npm audit screaming about vulnerabilities in packages buried so deep in your dependency tree you need a fucking archaeology degree to find them.

The real win isn't speed - it's that when shit breaks at 2AM, Stack Overflow has 3 million answers and every monitoring tool just works. DataDog? Plug and play. New Relic? Just install the agent. No "we'll support that in v2" bullshit.

Deno: Security Theater with Real Benefits

Deno 2.0 fixed the npm thing but here's what they don't tell you: shit still breaks in weird ways. That package that assumes __dirname exists? Yeah, it'll fuck you. And Deno's permission system is great until you spend 4 hours debugging why your app can't read a config file and end up just using --allow-all like everyone else.

When it works though, it's actually pretty nice. Netlify runs Deno for edge stuff, Supabase uses it for user functions. The startup time is legit better, and not having to set up Jest/Mocha/whatever testing bullshit is refreshing.

Bun: Fast as Hell, Stable as a House of Cards

Bun's benchmarks aren't fake - it really is 2-4x faster for HTTP. The problem? It crashes. Not maybe-crashes, not edge-case crashes. Production API goes down at 2PM on Tuesday crashes.

We tried Bun in prod early 2024. Ran great for three weeks, then a concurrent build thing started crashing the API. Not JavaScript errors - actual segfaults. Good luck explaining to your PM that your runtime is dumping core like it's 1995.

The Reality Check Nobody Wants to Hear

Your shitty SQL queries and that API that returns 500s every Tuesday matter way more than Hello World benchmarks.

Just use Node.js unless you've got an actual problem. Like Lambda cold starts eating your AWS bill, or TypeScript taking so long to compile that devs have time to make coffee and rethink their career choices.

Node.js: 16 Years of "It Just Works" (Mostly)

Netflix didn't pick Node because it's fast - they picked it because it doesn't randomly die. PayPal, LinkedIn, Uber run their money-making stuff on Node because boring beats fast.

We run Express APIs with millions of requests. Biggest drama? Junior dev forgot to return early in a callback and created a memory leak that took three weeks to find.

Monitoring just works. PM2, DataDog, Prometheus - all plug and play. Memory spike? You get flamegraphs, not guessing games.

Node.js single-threaded event loop architecture handling asynchronous operations

Deno: Security First, Compatibility Second (Until Recently)

Before Deno 2.0, nobody used it except academics and security nerds. Now Netlify runs edge functions on it, Supabase uses it for user functions.

Deno's permissions aren't bullshit when you configure them right. We had a microservice handling PII, and --allow-read=/app/config --allow-net=api.internal.com stopped a supply chain attack cold. But debugging permission errors? You'll spend a week figuring out if it's --allow-read=/app/config vs --allow-read=/app/config/ vs --allow-read=/app/ because the trailing slash matters and the error messages are useless.

No node_modules is beautiful. Container goes from 200MB to 80MB because you're not shipping a small city of dependencies.

Bun: Benchmark King with Production Growing Pains

Bun's numbers aren't fake. HTTP is 2-3x faster, TypeScript compiles fast, package installs make npm look like dial-up. No webpack bullshit.

But benchmarks don't show segfaults. We tried Bun in prod early 2024. Ran perfect for three weeks, then a concurrent build crashed the API. Not a JavaScript error - a core dump. Like debugging C code but worse.

Teams running Bun in prod are either super careful (just Vite builds and testing) or insane (accepting random crashes for speed).

Container Reality Check

Docker container layers - runtime size matters until you add real dependencies

Node containers hit 150MB, Deno gets to 80MB, Bun squeezes to 50MB. Then you add your actual app, Postgres drivers, monitoring crap, and it's all 200MB anyway.

Runtime Performance Reality:

Bun: 52k+ req/sec, Node: 25k req/sec, Deno: 40k req/sec - but your database is still the bottleneck

Node.js: Security Through Operational Maturity (And Constant Vigilance)

npm Security Reality:

npm audit screams about critical vulns but 80% are bullshit that require you to already be owned

Node security is like Windows - fine if you know what you're doing and patch regularly. Problem is npm's security spam flooding your inbox. Last month: prototype pollution in lodash (again), path traversal in some CSV thing, ReDoS in a date lib buried six deps deep.

Half these "critical" vulns need the attacker to already own your box. Useful as tits on a bull.

Real security is operational: Snyk, npm audit, OWASP checks - you can scan and fix vulns. When event-stream got owned in 2018, tools existed to catch it.

Attack surface is huge - Node runs with full permissions by default. That npm package stealing SSH keys? It can read your whole filesystem unless you containerize.

Deno: Security Theater That Actually Works

Deno's Permission Model:

Granular permission system with --allow-net, --allow-read, --allow-write flags that actually stop supply chain attacks

Deno's permissions actually work - stopped a supply chain attack cold in our prod. Compromised package tried to phone home, --allow-net=api.internal.com said nope.

But debugging permission errors makes you want to punch walls. App can't read a config? Is it --allow-read=/app or --allow-read=/app/? Trailing slash matters, error just says "permission denied" without saying WHICH fucking permission, and you'll waste 2 hours guessing.

Most teams just use --allow-all in dev because life's too short, then panic on deploy day figuring out the real permissions.

Works great for microservices though. Payment stuff with --allow-net=stripe.com,database.internal --allow-read=/app/config means a compromised package can't steal your database.

Bun: Fast Compilation, Slow Security Progress

Bun's security story: "we're working on it." trustedDependencies helps a bit, but no sandboxing. Malicious package gets in? Full system access.

Worse: memory corruption bugs in the Zig runtime. Not JS errors you can catch - core dumps that might be exploitable.

Production Security Reality Check

OWASP Top 10 vulnerabilities - more dangerous than your runtime choice

Most prod security incidents? Not runtime bugs. SQL injection, auth bypasses, exposed Redis, unencrypted traffic - the usual dev fuckups.

Runtime choice matters for supply chain defense: Deno blocks packages, Node needs external scanning, Bun prays you don't install malware.

Compliance and Audit Reality

SOC 2 auditors get Node - docs exist, patterns are established, Helmet.js for security headers. Deno's model looks good on paper but explaining it to auditors sucks. Bun? Good luck getting compliance for a runtime that's been "stable" for 2 years.