>after their solution took down the whole system in cascading failures because it was returning 500 due to the non-serverless database not scaling

Why is a single dev able to take down your entire system without intention?

>They can write quicksort but have no idea

So don't use quicksort or identical questions and ask them more.

Your entire anecdote can just as well be held as testament of how a company's process is completely fragile. Which is at least a yellow flag as to what else it is hiding.