Suppose a web-server has a threshold to serve 10 requests, what shall happen when it receives the 11th request

I recently came across a system design question which asks --> What happens when a server with threshold of 10 request receives the 11th requests? Since i have very little knowledge , i would need some help.

Some queries in my mind regarding the design --> shall we use message queues? or may be a load balance with messaging queues.

Thanks in advance.