Static DNS will keep handing out an address after the application behind it is gone. Health checks make eligibility a measured fact, then a one-second TTL makes that fact usable.
Probe what you publish
Check the addresses you actually return, over the protocol that means up for that service — often HTTPS. Probing IPv4 only while publishing AAAA is how dual-stack surprises start.
Policy honours health
GeoDNS and weighted pools should exclude unhealthy endpoints automatically. A nearby region that is down is not nearby in any useful sense.
Alert anyway
DNS failover is not a substitute for knowing a region is down. Health checks decide answers. APM explains why.
Avoid flaps
Set sensitivity so a single blip does not churn records. Rehearse failure in staging until the DNS graph is boring.
