vercel-functions

Vercel Functions

You are an expert in Vercel Functions — the compute layer of the Vercel platform.

Function Types

Serverless Functions (Node.js)

• Full Node.js runtime, all npm packages available
• Default for Next.js API routes, Server Actions, Server Components
• Cold starts: 800ms–2.5s (with DB connections)
• Max duration: 10s (Hobby), 300s (Pro default), 800s (Fluid Compute Pro/Enterprise)

// app/api/hello/route.ts
export async function GET() {
  return Response.json({ message: 'Hello from Node.js' })
}

Edge Functions (V8 Isolates)

• Lightweight V8 runtime, Web Standard APIs only
• Ultra-low cold starts (<1ms globally)
• Limited API surface (no full Node.js)
• Best for: auth checks, redirects, A/B testing, simple transformations

// app/api/hello/route.ts
export const runtime = 'edge'

export async function GET() {
  return new Response('Hello from the Edge')
}

Bun Runtime (Public Beta)

Add "bunVersion": "1.x" to vercel.json to run Node.js functions on Bun instead. ~28% lower latency for CPU-bound workloads. Supports Next.js, Express, Hono, Nitro.

Rust Runtime (Public Beta)

Rust functions run on Fluid Compute with HTTP streaming and Active CPU pricing. Built on the community Rust runtime. Supports environment variables up to 64 KB.

Node.js 24 LTS

Node.js 24 LTS is now GA on Vercel for both builds and functions. Features V8 13.6, global URLPattern, Undici v7 for faster fetch(), and npm v11.

Choosing Runtime

Need	Runtime	Why
Full Node.js APIs, npm packages	nodejs	Full compatibility
Lower latency, CPU-bound work	nodejs + Bun	~28% latency reduction
Ultra-low latency, simple logic	edge	<1ms cold start, global
Database connections, heavy deps	nodejs	Edge lacks full Node.js
Auth/redirect at the edge	edge	Fastest response
AI streaming	Either	Both support streaming
Systems-level performance	rust (beta)	Native speed, Fluid Compute