Vercel Serverless Functions Guide

1. Install CLI — npm i -g vercel, vercel login 2. Deploy any repo — vercel (auto-detects Next.js/Astro/Static, creates preview URL) 3. Serverless function — api/hello.ts exports default function handler(req, res) 4. Edge function — export const config = { runtime: "edge" } for global low-latency 5. ISR — revalidate: 60 in getStaticProps, regenerates page in background 6. Env vars — vercel env add DATABASE_URL, separate dev/preview/production 7. Custom domain — vercel domains add example.com, auto HTTPS via Let's Encrypt 8. Production — vercel --prod or git push to main (auto-deploy on merge)

// api/users.ts — Node.js serverless function import { db } from "../lib/db"; export default async function handler(req: VercelRequest, res: VercelResponse) { if (req.method !== "GET") { return res.status(405).json({ error: "Method not allowed" }); } const users = await db.user.findMany({ take: 20 }); return res.status(200).json(users); } // api/geo.ts — Edge function (no cold start, runs in 19 regions) export const config = { runtime: "edge" }; export default function handler(req: Request) { const country = req.headers.get("x-vercel-ip-country") || "unknown"; const city = req.headers.get("x-vercel-ip-city") || "unknown"; return Response.json({ country, city, message: `Hello from ${city}, ${country}`, }); } // app/page.tsx — ISR (Incremental Static Regeneration) async function getStaticProps() { const posts = await fetch("https://api.example.com/posts").then((r) => r.json()); return { props: { posts }, revalidate: 60 }; // regenerate every 60s }