THE SWISS CHEESE MODEL, PT. 1

Summary from the TLDR Design newsletter

The Swiss Cheese model explains how major failures often result from several small, independent mistakes aligning rather than a single catastrophic error. A famous example is Knight Capital's $460 million trading loss, where outdated code, a reused software flag, an incomplete deployment, missing verification, and inadequate safeguards combined to trigger a company-ending failure. The key lesson is that robust systems rely on multiple overlapping protections, because any one small mistake is usually harmless until several failures line up at once.