DNS is a fragile system to use within a DC to do service/endpoint discovery. That's because DNS tends to be a single point of failure.
Though the DNS system can inherently be resilient, within a DC most people only operate a single DNS server because a hierarchical domain scheme and DNS setup within DC is too cumbersome and is much less reactive to end point changes.
Eg: Changing a service endpoint in an emergency takes way too long.
A single DNS server means, still there are propagation delays(local caches) and a single point of failure at critical moments(when there is a thundering herd)
That's a pretty weak argument. It's like calling a databases a single point of failure because the people who set them up tend to be too lazy to setup HA.
Though the DNS system can inherently be resilient, within a DC most people only operate a single DNS server because a hierarchical domain scheme and DNS setup within DC is too cumbersome and is much less reactive to end point changes. Eg: Changing a service endpoint in an emergency takes way too long.
A single DNS server means, still there are propagation delays(local caches) and a single point of failure at critical moments(when there is a thundering herd)