Yeah I think the premise is a bit poorly designed, I would just wave it away and focus on the queue. The coding problem itself is pretty well defined. And I think the premise is intentionally presented kind of poorly defined, which makes me think it's meant to not really be part of the problem.
> So, we decide to make our server's life easier by trying to ensure, from the client, that it doesn't ever have to handle more than one request at once (at least from the same client, so we can assume this is a single-server per-client type of architecture).
Which make the whole coding exercise moot.
What if there are 1 million users opening the browser at the same time?
The queue question is fun but doing it in the client is not right.