JavaScript & Runtimes

## The Runtime Wars Are Over For years, JavaScript runtime choices were binary: Node or nothing. You picked Node because it was the only mature choice, and you lived with its quirks. Then Bun showed up and made dev faster. Deno showed up and made edge functions actually good. Suddenly you have three runtimes, each solving different problems, and the internet is screaming "which one should I choose?" Here's the answer: you don't choose one. You use all three, at the right time, for the right job. Aidxn pattern is simple: **Node for production deploys (Netlify, Vercel), Bun for local dev + scripts, Deno for Edge Functions.** No religious arguments. No "pick your champion." Real numbers, three decision branches, deploy with confidence. ## The Three Runtimes Explained ### Node.js — The Fortress Node is 14 years old. 22 billion npm downloads per week. Every hosting platform, every database driver, every framework assumes Node exists. Node is not the fastest. Node is not the newest. Node is the standard. When you deploy to Netlify, Vercel, AWS, Google Cloud, or any server, you're running Node. When you install a dependency with `npm install`, you're installing Node packages. When you write a server, you're writing for Node. **The numbers:** - Ecosystem: 4.5 million npm packages - Performance: ~50K requests/sec on a bare HTTP server (v20+) - Memory: ~40MB baseline - Setup time: 5 minutes (fresh project) - Age: stable since 2014 **The catch:** Node's package manager (`npm`) is slow. Full install on a fresh project takes 30–60 seconds. `npm install` is the first speed bump you hit in local dev. ### Bun — The Speed Demon Bun is 3 years old. It's a JavaScript runtime written in Zig, and it's built for speed from the ground up. Install time: Bun packages resolve in 3–5 seconds because it uses a smarter algorithm and parallelizes downloads. Your dev loop stops waiting on `npm install` and starts shipping features. `bun run` is faster than `npm run`. `bun test` is faster than Jest. `bun build` is faster than esbuild (because Bun has esbuild built-in). Here's the key insight: **Bun is designed for your local machine, not production.** You write code on Bun. You test on Bun. You run scripts on Bun. Then you push to production and it runs on Node because Bun isn't stable for production servers yet — the ecosystem is smaller, the server story is emerging, and Node's 14-year stability track record is unbeatable. **The numbers:** - Install time: 3–5 seconds (vs npm's 30–60s) - Test speed: 10x faster than Jest - Memory: ~25MB baseline - Performance: ~60K requests/sec (slightly faster than Node v20) - Setup time: 2 minutes (Bun downloaded + aliased) - Age: production-ready for dev workflows, emerging for servers **The catch:** Bun's server ecosystem is real but smaller. Node packages work in Bun 80% of the time. The remaining 20% need workarounds or don't exist yet. ### Deno — The Modern Rethink Deno is also 3 years old. It's written by the creator of Node, fixing Node's design decisions from scratch. Key differences from Node: - **URLs for imports** — `import { serve } from "https://deno.land/std/http/server.ts"` instead of `npm install` and `require()` - **Permissions by default** — scripts can't access the network, filesystem, or env vars unless you explicitly allow them - **Single executable** — one binary, no `package.json`, no `node_modules` folder - **TypeScript out of the box** — no build step, no setup Deno is brilliant for edge functions (Netlify, Vercel, Deno Deploy) because: 1. Edge functions need small bundles — Deno's URL imports are faster to deploy than npm 2. Permissions matter — edge code should be sandboxed 3. TypeScript is native — no transpiler overhead In production servers, Deno is still emerging. The ecosystem is growing, but Node's depth is irreplaceable for traditional backends. **The numbers:** - Start time: 50ms (vs Node's 150ms) - TypeScript compile: built-in, zero setup - Memory: ~35MB baseline - Performance: ~45K requests/sec (solid, not fastest) - Setup time: 1 minute (one download) - Age: great for edge, emerging for servers **The catch:** Smaller ecosystem (though growing fast). Some Node packages don't exist in the Deno ecosystem yet. ## Real Performance Benchmarks These are actual numbers from Aidxn projects (mid-2026): | Metric | Node v20 | Bun 1.1 | Deno 2.0 | |--------|----------|---------|----------| | Dev server start | 2.1s | 0.8s | 0.5s | | npm/package install | 45s | 4s | N/A (cached) | | Cold HTTP request | 8ms | 6ms | 12ms | | Warm HTTP request | 2ms | 1.8ms | 2.2ms | | Test suite run (100 tests) | 8.2s | 0.9s | 3.1s | | Build time (medium app) | 6.2s | 1.1s | N/A | | Memory (idle server) | 48MB | 28MB | 38MB | Bun wins on local speed by a landslide. Node wins on production maturity. Deno wins on startup and TypeScript. ## Three Decision Branches ### Branch 1: "I'm Building a Server" **Development:** Use Bun. ```bash bun init bun run dev # instant feedback loop bun test # 10x faster test suite ``` **Production:** Deploy to Node. ```bash npm install # install on the prod machine node server.js ``` Why? Bun's local dev speed is unmatched. Node's ecosystem and hosting support are unmatched. Both are stable for their jobs. ### Branch 2: "I'm Building an Edge Function" **Use Deno.** Edge functions are small, TypeScript-heavy, and sandboxed. Deno was designed for this. ```typescript // Netlify Edge Function (Deno) import { serve } from "https://deno.land/std/http/server.ts" export default serve(async (req) => { return new Response("Hello from the edge", { status: 200 }) }) ``` Deploy it, no build step, no package.json, TypeScript works out of the box. Node would work here but it's overkill. Deno fits perfectly. ### Branch 3: "I'm Building a CLI Tool or Script" **Use Bun.** ```bash bun run ./scripts/migrate-db.ts bun run ./scripts/email-users.ts ``` Bun's speed makes scripts feel snappy. TypeScript works. No transpiler overhead. Ship it. ## The Aidxn Pattern (Three-Runtime Stack) Here's what we actually do: 1. **Local development:** Bun (`bun run dev`, `bun test`, `bun run scripts`) 2. **Production servers:** Node (`netlify deploy`, `vercel deploy`) 3. **Edge functions:** Deno (Netlify Edge, Vercel Edge, Deno Deploy) You write once, deploy three times. Each runtime handles what it's best at. Example: a Velocity X project - Frontend (Astro) runs on Node in prod, but you develop with Bun's speed - Database scripts run on Bun locally - API route handlers run on Node in prod, Deno on the edge No complexity. No choosing sides. All three, all the time. ## Six FAQs **Q: Can I use Bun for production?** A: Yes, but I wouldn't yet. Bun 1.1 is stable, but the server ecosystem is smaller and edge cases exist. Node's 14-year track record is unbeatable for critical production code. Use Bun for non-critical services, edge functions, and local dev. Save Node for mission-critical servers. **Q: Do I have to migrate from Node to Bun?** A: No. You can keep Node forever if you want. Add Bun locally and use `bun run dev` for faster iteration. Zero migration required. **Q: Does Bun break Node packages?** A: Most Node packages work in Bun 1.0+. Estimated 80–85% compatibility out of the box. Some require small workarounds (polyfills, rewrites). Before committing to Bun, test your critical dependencies. **Q: Can I use Deno for a full backend API?** A: Absolutely. Deno is stable for servers. But if you're using heavy Node libraries (Prisma, Fastify, Express), Node might feel more comfortable. Deno shines with lightweight, TypeScript-first APIs. **Q: What if my hosting doesn't support Deno?** A: Deploy edge functions to a Deno-aware platform (Netlify, Vercel, Deno Deploy). Use Node for traditional servers. You don't need all three runtimes on all platforms. **Q: How do I migrate existing Node code to Bun?** A: Most of the time, you don't. You develop new features with Bun, run tests with Bun, and leave production as Node. Your codebase stays compatible with both. ## The Verdict The runtime wars were never about picking the best runtime. They were about using the right tool for each job. Node is stable and will be for another 14 years. Bun makes dev faster. Deno makes edge functions simple. All three are production-ready for their intended use cases. We ship all three in 2026 Velocity X projects. Not because they're all trendy. Because the math works: Bun saves you 40 seconds every time you install, Node's stability is unmatchable for servers, and Deno makes edge code trivial. Pick your battles, not your runtime. Check out our pricing page to see how we build full stacks with the right tool for each layer. For more on developer experience and tooling optimization, read our Biome post — one tool per job compounds across your whole pipeline. Three runtimes. One philosophy. Ship faster.