Comparisons
Pairs that get conflated in real conversations. Neither column wins — what decides is the situation. Each record leads with the confusion, because the confusion is the reason the record exists.
Outcome vs outputFirst version vs prototypeDecision record vs one-pagerSuccess metric vs guardrailReversible vs irreversible decisionsFeature flag vs long-lived branchNumbers vs conversationsIncident vs bug
Success metric vs guardrail
What people get wrong about this pair
A team picks a success metric and wins it: checkout conversion rises because the address form lost its validation, and the failed-delivery rate doubles a month later. Without a guardrail the win is reported and the loss is discovered by support.
Success metric
Use it when
The one number that should move when the product gets better.
Guardrail
Use it when
The numbers that must not get worse while you move it.
| Aspect | Success metric | Guardrail |
|---|---|---|
| Direction | Up (or down) is the goal | Must stay within a band |
| How many | One | A few, chosen from what the change could break |
| Decides | Whether to invest more | Whether to ship at all |
| Typical failure | Optimised by gaming it | Never defined, discovered by support |