I have written applications that are very small scale and the code I write works fine for them. But I have often wondered how the server side code I write would scale up from 100s of queries per day to millions.

Also when looking at possible jobs/projects, people are often looking for developers with experience in this sort of high traffic database design so I would at least like to be able to say, I havent gotten to work on a project that was this popular, but I at least have tried to simulate it.

Are there tools or frameworks that can generate a lot of traffic or at least simulate what would happen with traffic on different orders of magnitude so I could get some practice writing optimized code for higher traffic applicaitons?