Knight Capital — $440M in 45 minutes

Casualty stat: $440M lost in 45 min · firm bankrupt

A retired feature flag named 'Power Peg' was repurposed for a new SMARS router. Eight servers got the new code; one didn't. On market open, the unupdated server ran Power Peg's 9-year-old logic against live orders, blasting market-makers with errant trades. By the time the team isolated the bad server, Knight had eaten a $440M loss and would be sold inside a year.