"Tell me about your biggest failure." Amazon tests this because they value learning over perfection.
Bad answer: disguising a success as a failure. "I worked too hard." Interviewers see through this immediately.
Good answer: "I designed a caching layer that caused stale data for hours before we caught it. I didn't load-test with realistic data patterns. After that, I created a pre-launch checklist that our team still uses. The next launches had zero caching incidents."
Show the failure, the lesson, and the lasting change you made. Growth beats perfection.