Someone asked a similar question a few years ago and there was a good discussion on HN about it here. https://news.ycombinator.com/item?id=4446880 https://news

Someone asked a similar question a few years ago and there was a good discussion on HN about it here. https://news.ycombinator.com/item?id=4446880 https://news.ycombinator.com/item?id=4446880 My father's entire career revolved around IBM's TPF mainframe systems. Airline Reservation Systems, Credit Card Processing, and the IRS use it for extremely high volume processing.