First sorry for delayed answer. If I googled correctly lac should be order of 100.000. If you mean 100.000 request per second then most likely one server will not be able handle all this. Just to outline biggest issue with high request load (this is not primarily MonoX issue, but asp .net in general) and that's thread per request philosophy. This means that each thread will handle one request from start to end. Threads are relatively expensive resource so usually it's limited to certain number, when you run out of threads any request will have to wait even it will be served extremely fast. When you're not having any IO bound(db, network or file access) actions this is usually not a problem and your hardware would be most likely the limit. But if you have IO bound actions that are very slow compared to processing speed your threads are doing nothing just waiting for IO operation to complete and are blocking any other request for processing. You can have multiple web servers in web farms to tackle this issue, the load balancer in front of them will take care of spreading the load over them. But keep in mind that web farm will introduce some performance penalties as you can't keep any shared resources in local storage any more (session, cache, file system), so you would have to use distributed systems that every web server can access. You would need to do stress tests on your system to find best configuration (you can play with asp .net settings on number of threads and concurrent requests it should handle to better utilize you web server hardware) and number of servers you should have to handle to load. One nice thing with farms is you can easily add another node, especially when in the cloud, you can bring it up in few minutes.
Now this is all fine if your database can handle the load. If database starts to crack under volume of data, you can't just add nodes to solve the problem as each node will be slow. If you're having huge amount of data you need to serve db is almost certainly going to start to drag application. And there is really no simple solution to these issues and it should be solved base on data use case.
To recap if your database can handle the load it should be possible to configure site to handle high load. If db can't handle the load then you're going to have a hard time fighting these issues on MonoX. Anyway you should do a stress tests to really see if it's going to work as I might easily miss something in the equation.