async function handle(req) {
  // Send the request to `origin_0`.
  const resp = await fetch(req, {
    backend: "origin_0"
  });

  // Cache-Control: no-store prevents browsers from writing the object to disk.
  // We add 'private' in case there are any public caches downstream of Fastly,
  // between us and the browser, which might perform request collapsing on public content
  resp.headers.set("cache-control", "private, no-store");

  // Remove all other caching-related response headers
  resp.headers.delete("expires");
  resp.headers.delete("etag");
  resp.headers.delete("last-modified");

  return resp;
}

addEventListener("fetch", event => event.respondWith(handle(event.request)));