NIS is a good one. I have UUCP as a skill on my resume as an easter egg but no one ever asks about it.

For DNS, my favorite interview question goes like this,

How would you verify DNS is resolving from within a pod on Kubernetes?

After listening to the answer, add some constraints:

1. Common networking utilities like ping, nslookup, dig, etc are not available

2. Container user is unpriviledged

3. su/sudo do not work

This can lead to some elaborate k8s troubleshooting or the simple, and correct, answer of getent hosts.