How Forgotten Code Cost Knight Capital $440 Million in 45 Minutes

Knight Capital's catastrophic loss demonstrates that in high-frequency trading, dead code isn't just technical debt—it's a systemic risk capable of destroying a firm in minutes. The firm's failure to automate deployment verification and implement emergency controls allowed dormant code from 2003 to activate accidentally, causing $440 million in losses and becoming the SEC's first enforcement case under the Market Access Rule. This disaster fundamentally transformed industry practices around code cleanup, deployment automation, and emergency shutdown procedures.