I did say that those aspects of Ruby would start to be painful at that scale, not that it was totally unusable. Clearly it's usable, and there's certainly less

I did say that those aspects of Ruby would start to be painful at that scale, not that it was totally unusable. Clearly it's usable, and there's certainly less scale-able things than Ruby on Rails out there serving big production traffic today. But I wouldn't recommend switching an app that big in some other language over to Ruby, and at least as many companies have moved off of Rails monoliths when they outgrew them, like AirBnB for example.