Bun 1.0: Fast Is a Feature, Compatibility Is the Question
Bun hit 1.0 this month, positioning itself as a drop-in Node replacement that's also a package manager, bundler, and test runner — one binary, everything fast. I've run it on side projects since the beta. The speed claims hold up; the question is everything else.
The speed is real
On our mid-size monorepo: bun install in 1.9s where npm install takes 34s (cold). The test runner cleared a Vitest suite in roughly a third of the time. Startup latency — bun run script.ts — is nearly instant, and TypeScript just executes, no ts-node, no build step:
bun run migrate.ts # TS, no compilation ceremony
bun test # Jest-compatible expect() built in
bun install # reads package.json, writes bun.lockb
That combination quietly changes daily ergonomics: scripts, one-off tools, and CI setup steps all lose seconds that were pure friction.
Where I use it today, confidently
- Package installation, even for Node projects — it's compatible with
package.jsonand dramatically faster in CI. - Scripts and internal CLIs — instant TS execution makes it the best scratchpad runtime.
- Tests for libraries without heavy Node-API dependencies.
Where I still deploy Node
Bun implements most of the Node API surface, but "most" is doing work in that sentence. We hit gaps in less-traveled corners: a native module needing node-gyp quirks, subtle http behavior differences behind a proxy, an ORM whose driver assumed Node internals. Each individually fixable; collectively they're why my production servers stay on Node LTS this year. Fast is a feature — but boring is also a feature, and production loves boring.
The strategic read
Even if you never deploy Bun, its existence already paid dividends: Node shipped its own test runner, npm is under pressure on speed, and the ecosystem is re-learning that developer tools can be fast. Adopt it where blast radius is small, watch the compatibility tracker, and re-evaluate in six months — the trajectory is steep.