On: Why is it faster to process a sorted array than an unsorted array? (2012)

[wongarsu]

If you are looking for someone to work on performance-critical code, you would probably prefer someone who has already learned this.

Apart from being useful knowledge for the job, it's a good indicator, showing if the person has worked on such problems before (or alternatively has good knowledge to tackle such problems)

[skybrian → wongarsu]

Yes, I'd prefer them but only slightly.

If they don't know it, they're not an expert. But did they claim to be, and how quickly could they learn?

If they do know it, it doesn't mean they're an expert either. It's easy to learn these things just by happening to read about them.