Bun released 1.0 in September 2023. Three months later we tried it in dev on an internal app (Express + Prisma + 14k LOC TypeScript) and on a mid-size Next.js project.
Install
bun install did npm install's job in 4.2 seconds vs 38. A 10x factor. On CI builds for big projects, this alone pays the transition.
Test runner
The API is nearly identical to Vitest/Jest. Our 480-test suite ran in 6.1s on Vitest. On Bun: 2.4s. No magic, just fast.
Runtime
Running the Express app with bun run start we got +35% throughput on a synthetic benchmark. In production the gap is smaller because the bottleneck is almost always the database, not runtime CPU.
What does not work yet
- Native modules: some N-API-dependent packages (sharp, bcrypt) had workarounds in 1.0; better now, still verify.
- Cluster mode / worker_threads: parity with Node not yet complete.
- Production hosting: at end of 2023 nearly no PaaS (Vercel, Railway, Fly) natively supports Bun. Docker works, less convenient.
Verdict
For dev experience: already today. bun install and bun test are the first change we make in our repos. For production: we wait until mid-2024, when host support matures and our experience is firmer.