La couche des dangers, sans avoir à construire le réseau

const API = "https://api.cudatus.com";

// on your server — the key stays here
const { ticket } = await fetch(`${API}/v1/stream/tickets`, {
  method: "POST",
  headers: { Authorization: `Bearer ${process.env.RELAY_KEY}` },
}).then((r) => r.json());

// in the browser — a ticket, never the key. The disc follows the driver.
const stream = new EventSource(
  `${API}/v1/stream?lat=48.8698&lon=2.3078&radius=8000&ticket=${ticket}`,
);

// everything already live in the disc, once, on connect
stream.addEventListener("snapshot", (e) => replaceAll(JSON.parse(e.data).events));

stream.addEventListener("event", (e) => {
  // the delta is an envelope: created | updated | expired
  const { change, event } = JSON.parse(e.data);
  change === "expired" ? drop(event.event_id) : upsert(event);
});

// we always close on schedule; the ticket died long before
stream.addEventListener("bye", () => reconnectWithAFreshTicket());