Adding Queries to Existing High Traffic Adult Website

Hi, This project is only for very experience database experts! I run a succesfull EXISTING high traffic adult website. It's a website with tons of amateur content. The site is running on php mysql. Now I like to add about 25-30 categories in a pulldown menu. For these categories there have to be added queries. For example for the category "wife". The query have to show all galleries who have the word: wife, wives, milf, older, mature in the gallery description. The query results have to be displayed in the same order as how the daily galleries are displayed now, and you have to find an optimal way to execute the queries. The average Load Time now for the site is Very Fast (0.57 Seconds), 90% of sites on the www are slower. After the queries have been installed the fast load time must be maintained. Queries have been added in the past but never resulted in a stable system. Therefor I like to do a 1 week test to see if the database and server can handle the load. If not you have to advice me how to overcome this issue. Ofcourse I pay 100% but after that the test shows that the system is stable.