Building "Intelligent" Sites.
Most customers used to request "static" websites, just a colloction of webpages with the content to describe their businesses or institutions, that kind of requirements have shifted to require sites that "do things" like keeping track of the visitor from page to page, presenting specific information depending on the visitor's profile or where the visit is comming from. We have developed this way entire applications with different levels of authentication, dynamic content many times retrieved from a database.

Some application have involved complex searches in databases with hundreds of thousands of records, these applications were accessed by multiple concurrent users without a noticeable degradation in the performance of the website.