Ваш код живёт
там, где ваши пользователи

export async function handler(request, env) {
  const { country, pop } = request.geo;

  if (country === 'RU') {
    return Response.json({
      currency: 'RUB',
      warehouse: 'msk-1',
      servedBy: pop
    });
  }

  return Response.json({ currency: 'EUR', warehouse: 'fra-2' });
}

import { router } from 'tessera:router';

export const handler = router()
  .get('/health', () => new Response('ok'))
  .get('/api/price/:sku', async (req, env) => {
    const price = await env.KV.get(`price:${req.params.sku}`);
    return price
      ? Response.json(JSON.parse(price))
      : new Response('not found', { status: 404 });
  })
  .post('/api/order', order)
  .fallback(() => new Response('no route', { status: 404 }));

export async function handler(request, env, ctx) {
  const key = 'rates:' + new Date().toISOString().slice(0, 13);
  const hit = await env.KV.get(key, 'json');
  if (hit) return Response.json(hit, { headers: { 'x-cache': 'HIT' } });

  const fresh = await fetch('https://rates.internal/latest').then(r => r.json());
  // запись не блокирует ответ пользователю
  ctx.waitUntil(env.KV.put(key, JSON.stringify(fresh), { ttl: 3600 }));

  return Response.json(fresh, { headers: { 'x-cache': 'MISS' } });
}

$ tessera deploy --prod
$ curl -s https://shop-api.tessera.dev/api/price/TS-2049 \
    -H "authorization: Bearer tsr_live_••••••"

# x-tessera-pop: dme1
# x-tessera-exec: 4.1ms
# {"sku":"TS-2049","price":12490,"currency":"RUB"}