This is a server-side caching engine I wrote a little while back. I've kept it to myself for a while, but it's actually quite useful so I thought I'd share it here.
Basically it caches preprocessed and gzipped file content and reruns the preprocessing and gzip compression steps each time the underlying file is updated. You can specify custo m preprocessor functions for various files. Sowhen a client requests a cached file, it will instantly serve it the fully processed, compressed file. This is great for doing on-the-fly preprocessing like compiling less or sass stylesheets, adding preprocessing effects to images, etc...