What is the principle of 'fail fast'?

• A. Fail fast by lingering on issues
• B. Detect failures early and clearly so defects are found quickly and can be fixed promptly
• C. Allow failures to go unnoticed to maintain uptime
• D. Delay error reporting to users

Answer: (B)

Fail fast means detecting a problem as soon as it happens and signaling it clearly. This quick, explicit feedback lets defects be found quickly and fixed promptly, reducing debugging time and preventing bad state from spreading through the system. It relies on validating inputs and invariants early, and delivering a clear error or exception at the moment a violation is detected. For example, checking function inputs at the start and raising a precise error if something is invalid stops further processing and points directly to the cause. In tests and production, a failure should be reported immediately so developers can diagnose and remedy it right away. Delaying error reporting or letting failures go unnoticed hides problems, makes debugging harder, and increases downtime.