about caching: in the framework i'm developing i have a cache module which allows to use either a file cache as a backend or memcached. the file caching was written by myself, but i'll probably rewrite it with Cache::FileCache.

the advantage is that you can use file caching and don't need to set up a memcached server, but as soon as you need to scale your application and have more than one server, you can switch to memcached without changing anything but the configuration.