A great starting point is "designing data-intensive applications". Then you can read about various designs here and there.

But you don't need to go that very deep. What they ask is very specific and (unfortunately) you're better off going through 10-20 typical interview questions and their solutions.

Typical questions are "how would you design Google News/Twitter/...". There are many resources available, all of this is discussed on leetcode or interview preparation sites.

It's not hard, but I'd recommend to prepare for this well-before your interviews.