I had to shoehorn a bunch of functionality into a shopping cart system for Ruby on rails called spree. I think it's named something else now. The items could b

I had to shoehorn a bunch of functionality into a shopping cart system for Ruby on rails called spree. I think it's named something else now. The items could be extremely customized and that became very difficult, including things like calculating the cart price. It also felt like the most fragile system I wrote, but to my knowledge it's still running about six years later. The majority of my web work, though, was not very technically challenging.