Accessing dynamic links in the format of domain.com/<dynamic_page_name>

I am using code Igniter for my PHP project. I want to give provision in my site such that users can create new pages of their own, and access them directly from www.domain.com/<their_page_name>.

But, my developers have raised a concern that, 1000's of dynamic links that are presented in the format of domain.com/<page_name> is "not good for site's performance". For some 10-15 pages, it is fine. But, beyond that, it would effect the site's performance.

So, they proposed that the URL format should be like www.domain.com/something/page_name (here, 'something' is the controller name)

But, I really can't sacrifice my framework nor my requirement. Is there any way that I can achieve the format of "www.domain.com/<page_name>" without effecting the site's performance?

Thanks a lot for the help