npm install @vercel/functions

import { ipAddress } from "@vercel/functions";

export function GET(request: Request) {
  const ip = ipAddress(request);
  // Returns the real client IP, handles Vercel's proxy headers automatically
  return Response.json({ ip });
}

import { geolocation } from "@vercel/functions";

export function GET(request: Request) {
  const { city, country, region, latitude, longitude } = geolocation(request);

  return Response.json({
    message: `Hello from ${city}, ${country}!`,
    coords: { latitude, longitude },
  });
}

import { waitUntil } from "@vercel/functions";

export async function POST(request: Request) {
  const body = await request.json();

  // Send response immediately — don't make the user wait
  const response = Response.json({ status: "ok" });

  // This runs AFTER the response is sent, up to the function timeout
  waitUntil(
    logAnalyticsEvent({ event: "form_submitted", data: body })
  );

  return response;
}