Fail-Safe

A design principle where system failure defaults to a safe state rather than a dangerous one. A circuit breaker that trips during overload (cutting power rather than allowing fire), an elevator brake that engages when the cable breaks, a nuclear reactor that shuts down when cooling fails. The opposite—'fail-deadly'—means failure cascades into catastrophe. Fail-safe design accepts that failure is inevitable and focuses not on preventing failure but on ensuring that failure doesn't produce irreversible harm.

When to use it

When designing any system where failure has significant consequences; when evaluating existing systems for catastrophic failure modes; when the cost of failure is much higher than the cost of adding safety mechanisms; when building anything where human error is likely (always).

How it can help

Apply fail-safe thinking to every system you design: what happens when this fails? Financial fail-safes: stop-loss orders, emergency funds, insurance. Organizational fail-safes: escalation protocols, approval gates for irreversible decisions, automatic rollback mechanisms. Product fail-safes: graceful degradation, data backup, undo functionality. The key question isn't 'will this fail?' (it will) but 'when it fails, what happens next?'—and designing that 'next' to be safe rather than catastrophic.