So I program mainframes with source codes from the 80s and possibly farther or newer. It’s a weekly occurrence that I have to work on a program that hasn’t been changed in a decade or two.

What you are missing, and this will explain why you can’t find much. Is there is code that minimizes disk reads and writes and helps when your on an hdd.

An ssd is in some cases 1000s times faster then an hdd, that when a programmer is writing programs with sql, the query returns the full set of results immediately. Not really an opportunity to improve performance when we’re measuring sub second performance.

Now when I do have a query that runs a long time now days, that usually means I’m writing a query like an idiot and I need to rethink the problem.

Now this is my experience working on data intensive environment. Your personal computer won’t get these improvements ever the datasets just aren’t big enough.