Meta Final Round, Anyone have advice on Product Architecture Design interview?

I feel like I'm not explaining this well, but the interview is a back and forth conversation. The more fluid it goes, the better! You can't build full Instagram replica from scratch in 45 mins - no one can. So you start with a lot of simplifications and assumptions, and then as the interview goes on the interviewer will start adding in realistic things you might want on Instagram for real. They might even ask YOU to come up with ideas. (This is where the "product" comes from in "product architecture"). So if your whole system is kind of Twitter-like, and everything is public. Maybe you add the option to have "people I follow" only see a post and talk through how that might impact everything. I was in hours and hours and hours of conversations about privacy at Meta, and you also won't solve that in 45 mins either. Which is why it's about this back and forth process of demonstrating how you think about these concepts and not just if the answer is right. For example: "Well there's one way to add privacy and it's X followed by 5 mins of memorized speech" - you'll fail. Talking about several options and asking for the person's opinion - listening - and adapting well, is what they want to see.