What is the difference between a primary metric and a guardrail metric?

Tests whether you can separate the success metric you optimize from the safety metrics you protect in A/B testing. A strong answer defines the primary metric as the target business outcome, defines guardrail metrics as thresholds that must not degrade, and walks through a concrete scenario where a primary metric lifts but a guardrail metric drops enough to block the launch. Red flag: treating guardrails as nice-to-have secondary outcomes rather than hard constraints, or conflating them with secondary success metrics.