it sounds fine to me, if your DO is not getting overloaded

const doid = env.MY_DO.idFromString(user_id)
const stub = env.MY_DO.get(doid)

const doid = env.MY_DO.idFromString(user_id)
const stub = env.MY_DO.get(doid)

const stub = env.MY_DO.get(user_id) // ID
// or, for names
const stub = env.MY_DO.get(user_id, "name") // like KV's type

const stub = env.MY_DO.get(user_id) // ID
// or, for names
const stub = env.MY_DO.get(user_id, "name") // like KV's type

// Global list to store all active WebSocket connections
const clients = new Set();

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request));
});

async function handleRequest(request) {
  const upgradeHeader = request.headers.get('Upgrade');
  if (!upgradeHeader || upgradeHeader !== 'websocket') {
    return new Response('Expected Upgrade: websocket', { status: 426 });
  }

  const webSocketPair = new WebSocketPair();
  const [client, server] = Object.values(webSocketPair);

  // Add the new connection to the global list
  clients.add(server);
  server.accept();

  // Handle incoming messages
  server.addEventListener('message', event => {
    console.log('Message received from client:', event.data);

    // Broadcast the message to all connected clients
    clients.forEach(client => {
      if (client !== server && client.readyState === WebSocket.OPEN) {
        client.send(`Broadcast: ${event.data}`);
      }
    });
  });

  // Handle connection close
  server.addEventListener('close', () => {
    console.log('Client disconnected');
    // Remove the connection from the global list
    clients.delete(server);
  });

  return new Response(null, {
    status: 101,
    webSocket: client,
  });
}

// Global list to store all active WebSocket connections
const clients = new Set();

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request));
});

async function handleRequest(request) {
  const upgradeHeader = request.headers.get('Upgrade');
  if (!upgradeHeader || upgradeHeader !== 'websocket') {
    return new Response('Expected Upgrade: websocket', { status: 426 });
  }

  const webSocketPair = new WebSocketPair();
  const [client, server] = Object.values(webSocketPair);

  // Add the new connection to the global list
  clients.add(server);
  server.accept();

  // Handle incoming messages
  server.addEventListener('message', event => {
    console.log('Message received from client:', event.data);

    // Broadcast the message to all connected clients
    clients.forEach(client => {
      if (client !== server && client.readyState === WebSocket.OPEN) {
        client.send(`Broadcast: ${event.data}`);
      }
    });
  });

  // Handle connection close
  server.addEventListener('close', () => {
    console.log('Client disconnected');
    // Remove the connection from the global list
    clients.delete(server);
  });

  return new Response(null, {
    status: 101,
    webSocket: client,
  });
}