how to queue websocket events when a user is offline, and forward them to their next login?

I have an application with an authentication and list management system. The application uses React in front-end and Express/Mongo in back-end A user can add an item to another user's list that is stored in BDD in a list attached to a user.

I manage to get a notification to be sent to a specific user that a new object has been added to their collection, and get the notification.

  socket.on("sendNotification", ({ senderName, receiverName, type }) => {
    const receiver = getUser(receiverName);
    io.to(receiver.socketId).emit("getNotification", {
      senderName,
      type,
    });
  });



  useEffect(() => { 
    socket.on("getNotification", (data) => {
      setNotifications((prev) => [...prev, data]);
    });
  }, [socket]);

But if the receiver user is not logged in, the notification is lost.

how to queue websocket events when a user is offline, and forward them to their next login?