在web应用程序中缓存适量的数据——DB还是平面文件?

A web app I'm working on requires frequent parsing of diverse web resources (HTML, XML, RSS, etc). Once downloaded, I need to cache these resources to minimize network load. The app requires a very straightforward cache policy: only re-download a cached resource when more than X minutes have passed since the access time.A web app I'm working on requires frequent pars