Given HN's demographics, I'm probably older than most here. I've worked with and personally invented quite a few great products, usually spanning Product, UX, and Engineering work. It's a joke to pretend ageism isn't a thing, and asking questions that only a recent CS grad is going to remember is not a tacit form of filtering for age. There's not many technical questions a fairly smart, non-lazy person with some experience can't either find with a Google search, a conversation with a peer, or a bit of hacking to figure it out. It's been a LONG time since I had to write the code to invert a binary tree, but I've done stuff orders of magnitude more tricky and valuable than that countless times, as have many others. What makes a great engineer? I've lost count of how many times I've had to rewrite the code of many engineers who aced the 'whiteboard shuffle', then wrote hopelessly over-complex and unmaintainable garbage. Most of software engineering is not that hard from a 'learn the things or look them up to get stuff done' perspective. What's hard is working well with others and consistently emitting tight, semantic, legible code that's fun to look at and extend.