The "Quick checkout" extension is VQMOD based extension that reduce step of checkout process. This is very fast checkout process because there is only one step to checkout for registered customer, only choose payment method. For quest customer there are three steps. Enter basic info, billing info and payment method. The extension is useful for those who have no need to shipping method and shipping address. There is only one vqmod file that override core files and no need to modify in core files.