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Magic

ere long ago did a candidate state:

how does DNS work? why it works by magic

and did not elaborate. no teammate

did this candidate become, how tragic

True story. The job was for a position involving the day-to-day operation of DNS servers and firewalls involving DNS and client systems involving DHCP and DNS systems, and was a senior role so the ideal candidate would probably be able to say a little more than "magic" as to how DNS works. In hindsight the question was maybe too broad, though one might imagine someone who knows a bit about DNS either talking about it, or they might ask a counter-question to help get down into details. Like, "how long are you going to let me talk about DNS, because it could be a while to touch on getaddrinfo, the clever aliases used in DNS packets to save space, recursive servers, authoritative severs, how client systems obtain what DNS servers to talk to, root.hints, what glue records are, why a client might not use DNS (hosts file, DNS-over-HTTP, alternate resolution systems such as LDAP), why DNS might sometimes use TCP, and so forth." A good high-level summary of all this is of course "magic", which here means something like "it's complicated and there are a lot of fiddly details and you might want to abstract it away in some contexts, like when talking to people who do not need to know the details".

This magic crops up elsewhere, with folks stating variously that "analogue computing feels like magic for sure" and "while having a full amateur radio license and having studied comms engineering, still looks like magic".

A hard DNS problem: the owner of the zonefile added a new record that you requested. The serial number of the zone did increment (and there is no funny invalid wrap-around of the serial number going on (bonus points for knowing that)). The new record is not visible. What went wrong? This is probably too hard a question for a job interview, though you might explain all this and then ask how they would go about debugging the problem.