Vicky’s writeup is interesting, but to me the most interesting thing is Jeff Dean’s advice that sometimes doing a linear scan is the fastest approach (over any kind of indexing). This is basic advice, but modern developers might be pre-disposed to use index-based tools or data stores because the tech is now so good and ubiquitous.

Modern developers are predisposed to reach for off the shelf solutions, full stop. They're afraid of, or perhaps allergic to, just reading and writing files.

If you can learn to get past this you can unlock a whole universe of problem solving.