Also the fact that its written in Ruby on Rails probably doesn’t make it easier, performance wise.
How many non Ruby apps and all the databases and systems behind could climb their traffic 14x when they probably only perf-tested for a sustained 2-3x and, and paid for a profitable amount of rack space rather than a “lol, VC money, we’ll 10x later” amount of infra.
You load test and see how much it takes until the system falls over - basically you DDoS yourself and see what the numbers were when things broke, and what broke first second so on. Maybe in a sandbox maybe against prod.
It's very telling that issues began almost to the day of the Microsoft acquisition.