> An application developer (I'm leaving aside the can of worms opened by "web-app") absolutely should understand at least roughly how a red-black tree works.

Thanks for completely dodging any kind of substantive point I might have had. I can move the goalposts such that my opinion is always right and I can always win, too. But I generally try not to because that isn't the point of HN, at least as far as I can tell.

Here's my point. There are many, many software jobs. Only a fairly small subset of them need serious data structures and algorithms work. But interviews tend to focus on data structures and algorithms brain teasers, regardless of the actual day-to-day of the job.

I say "fairly small subset" here because that's the actual truth. There's a huge swath of programming that can get by magnificently with nothing more than arrays and hashtables.

I had a friend interview with Google to work in their uptime group or something like that. He had to solve some brainteaser about generating an in-order list of numbers that meet a certain criteria in O(n) time and constant space. I get that someone somewhere thought it was a good idea. But if you're tasked with keeping failures from happening being able to solve that brainteaser doesn't say anything about your suitability for the job. Being able to imagine disaster scenarios and how they'll play out seems a lot more important to me.

Now I'm not Google so who is to say that my opinion is right and theirs is wrong. Perhaps they're happier with the subset of folks who can do both. But it seems like they might well be missing out on the people who can imagine how bad it could get and help plan for that but who didn't take advanced data structures and algorithms.