About a decade ago I had a social media marketing platform (Wildfire) part of which was a special case web page builder. We scaled our engineering team in many

About a decade ago I had a social media marketing platform (Wildfire) part of which was a special case web page builder. We scaled our engineering team in many different ways, one of the many ways was to also contract external teams. One such team wrote a book based on code the wrote for us, Objects on Rails. The code was fine for a time, but we were increasingly serving traffic from Youtube which was a very popular platform for us at the time. The code in question could not scale in a cost effective manner for traffic coming from Youtube. In fact, it was stressing our ability to maintain a rational number of haproxy POPs - we'd have needed to massively change our operational architecture if the root problem could not be fixed. It took a while to identify, but eventually we found the exhibits abstraction to be the root of a number of significant and leaky performance problems (runtime object extension, blowing all method caches). I refactored out all of the uses of this code, replacing them with simple in-place conditionals in all cases. This dropped somewhere around 15kloc, and modified another 5k or so (I think these may be under-estimates, but I no longer have access to the code, and it's been a decade). We were able to deploy that patch with very few changes. The teams had done a good job of writing extensive end to end tests. It also helped that removing the abstraction resulted in far simpler code paths. I didn't need types to do this safely, the tests were sufficient. This is not to be a downer on typing extensions, but I think their advantages are often over-sold.