To modernize a running system, you have to duplicate everything so that you can someday do a switchover. For commerce tech, you switch, see what breaks, switch

To modernize a running system, you have to duplicate everything so that you can someday do a switchover. For commerce tech, you switch, see what breaks, switch back and adjust for next try. You may have lost some sales. But probably just inconvenienced people. When doing travel systems, something breaking is likely a lot of deaths.