So, I encounter a lot of programmers that have read a little and consider themselves to really know what they're talking about. However, they can't explain how an index works - not even in simple terms. Like, if I'm looking for someone with the username 'johnnygood', why would indexing the username column make that lookup faster? Even a very simplistic answer like, "an index orders the information so that the database server can jump to that record binary-search style rather than looking through every row" would be wonderful.

In that light, I think that programmers should know the basics of computer science: what references are; how a linked list works; a little about tree data structures; stacks, queues; basic sorting and searching stuff; etc. I'm not saying that you need to be able to talk about everything off the top of your head. I just think a familiarity with the theoretical concepts is good.

On the other end, I see a lot of people who know that PHP interprets strings using single quotes faster than double quotes, but have no idea why NoSQL might scale better (and might actively think it's because of the SQL language).

I want someone to say "a lot of the NoSQL technologies work by having you pre-compute data so that your data structures have the information you want to display together stored together in a structure that can be read more quickly like a hash." It isn't magic.