DNSSEC Signature Expiry — Days Until the Chain Breaks
DNSSEC signatures carry an explicit expiry date, and this check reports how much time is left on them. It is a narrower question than full validation and a more actionable one: a chain that verifies today tells you nothing about tomorrow, whereas a signature with four days of validity remaining is a scheduled outage unless something intervenes.
Why run it
Because the countdown is the only early warning that exists. Zone signing is normally automated, and automation that has stopped looks exactly like automation that is working right up until the last signature lapses. Checking remaining validity is how you tell the two apart. It is also the check to run immediately after any change to signing infrastructure, since a resigning process that was reconfigured last week may have been quietly failing ever since.
Why automate it
A one-off reading is nearly useless here, because the number is always decreasing and the point of interest is when it stops being refreshed. Sampled continuously, the shape is unmistakable: a healthy zone's remaining validity sawtooths upward on each resigning, while a broken one declines in a straight line to zero. That pattern is visible weeks ahead of the outage, but only if something is looking. Alerting on a threshold converts the most avoidable DNS failure into a routine maintenance task.
What it gives you
A countdown to a specific, certain outage, with weeks of notice. It is the difference between renewing signatures on a Tuesday afternoon and discovering the problem when half the internet can no longer resolve your domain.