It's worth noting that the source of this is a someone who is hawking a pricey "cracking the system design" type interview book. I feel like these types of post

It's worth noting that the source of this is a someone who is hawking a pricey "cracking the system design" type interview book. I feel like these types of posts are intended to create anxiety in the reader - "oh my god I had no idea what a quad tree even was?!" I think much of the cottage industry that has sprung up about "cracking interviews" is predicated on maintaining a constant state of anxiety as well. If you look at something like Leetcode it's the same thing, there's something like 2,000+ questions there. So many that you can never feel confident. The job of preparing is never done. As long as people have anxiety about everything they don't and can't have any sense of confidence, they will be inclined to fork over their money in an attempt to assuage that anxiety created by such material.