I think we're in agreement here; this is the part where I said "Several examples are so trivial that you'd be crazy to use an external database at all". For you

I think we're in agreement here; this is the part where I said "Several examples are so trivial that you'd be crazy to use an external database at all". For your shell history, you not only don't need indexes, you don't need the database either (as you conclude in the post). But if you're already in the database, it falls into that first "the index feature is right there" category. This HN thread is full of people skipping the index on their SQL tables in situations where I would write the index. Mostly I think people are just missing that you need to write indices in response to queries rather than what you're imagining when you first create the table.