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Express → Elysia (Bun)

medium

Elysia is built for Bun and gives end-to-end type safety with a Hono-like API. 10x+ throughput vs Express on the same hardware.

Estimated: 4-10h · 6 steps
Progress0%
Step 1: Install Bun and Elysia
curl -fsSL https://bun.sh/install | bash && bun add elysia
Step 2: Rewrite server entry
import { Elysia } from 'elysia'
new Elysia().get('/', () => 'ok').listen(3000)
Step 3: Convert routes

app.get('/users/:id', (req,res) => ...) → .get('/users/:id', ({ params }) => ...). Type inference for params/query/body via schema.

Step 4: Replace middleware

express.json() built-in. cors → @elysiajs/cors. helmet → @elysiajs/helmet. multer → @elysiajs/multipart.

Step 5: Add validation

Replace zod/express-validator with Elysia's TypeBox-based schemas: t.Object({ ... }). Errors are returned automatically.

Step 6: Run tests
✓ All endpoints respond identically. Benchmark shows multi-x throughput improvement.

What this migration involves

Moving from Express to Elysia (Bun) is rated medium and takes about 4-10h on a typical project. The guide breaks it into 6 steps, 2 of which ship with runnable commands and 1 with a verification check.

Express data →

Related migrations

Express → Fastify — medium, 4-12hExpress → Hono — easy, 2-4h

FAQ

How long does migrating from Express to Elysia (Bun) take?

Around 4-10h for a typical project — 6 steps, difficulty rated medium, 2 of them with copy-paste commands.

Is moving from Express to Elysia (Bun) reversible?

No reverse guide is tracked yet, so treat this as a one-way move and keep a full export of your Express data before you start.

What does Elysia (Bun) cost compared to Express?

Express: open-source from $0/mo, free plan available.