I didn't even know where to start, I mean, isn't maintaining a cache one of the trickiest problems around? I really didn't even know where to begin, because I'd never even considered building something like that myself... and who would? I said I'd keep track of file metadata and the time i added to files so i could expire them out of my cache. the feedback i got on that one was that i didn't seem interested in the problem, but it's more like i never thought about it before and didn't have any idea what they wanted me to tell them.