As part of T257527: automatically collect network error reports from users' browsers (Network Error Logging API), it'd be nice to have a way to serve a DNS record that was backed by an edge datacenter different than the "usual" datacenter for any given user. This is because if a user needs to send a Network Error report, it very likely means something is wrong with their route to the usual edge DC.
This isn't a strict requirement; browsers are supposed to buffer these reports and try again later in the event that sending them immediately fails. But it would help us receive reports in a more timely fashion, which would let us react and try to fix things.
It seems it's likely that a small patch can be made to add a skip_first flag at the resource level in gdnsd, which would save us defining and maintaining multiple flavors of country-to-datacenter maps in the dns repo.
An alternative approach might be to take an entire mapping and reverse it, but that's not as straightforward given the codebase.