Passing Checks Can Hide How Little Room Systems Have Left

A nightly job that once finished in 41 minutes now takes 88 minutes against the same 90-minute window, yet both results show as a pass on the dashboard. The article argues that pass/fail reporting discards the margin, meaning the distance between current performance and the point of failure. It recommends expressing margins in the units of what varies, such as time until a limit is reached, rather than as percentages. The piece distinguishes three types: headroom for capacity, tolerance for correctness, and freshness for how long evidence remains valid. It notes that tolerance and freshness erosion often goes unnoticed because no alert fires while the figures are still inside their thresholds.