i was thinking about doing just that - when request comes, check local file, if not present, fetch from remote url. but the problem is with large files(GBs) tha

i was thinking about doing just that - when request comes, check local file, if not present, fetch from remote url. but the problem is with large files(GBs) that you cannot serve as fast and the client has to wait instead of being redirected to the source which bypasses the cdn node and then what? you have to somehow get the large files too in a way that makes sense.