There's a difference between basic optimization, and needing to refactor most of your business logic because your assumptions about databases are boneheaded.

In general, it doesn't matter what you're doing, your basic design patterns need to fit around how a database works. If you don't know this, you'll hit scalability issues far too soon, and it'll take too long to fix them.

> Optimize your SQL query performance after you've released and proven that it's an actual bottleneck.

I've seen one project fail because the design patterns around using the ORM were incorrect. Then I joined another project where the bottleneck (from incorrect use of the ORM) was so bad the product couldn't scale beyond being a demo. It took 2 months to refactor, all because one of the programmers used an ORM incorrectly to save a few hours at the beginning.

If you know SQL you can get the best of both worlds though. You still use the ORM for basic queries, but if you know you need to, you can apply optimisations like eager loading basically for free (dev time wise). The issue is devs not understanding what's going on underneath creating unnecesary performance problems