As an interviewer, my job is to differentiate between people who have experience vs people who have just read books and articles. I interview mostly L6+, so I will not recommend people who I don't believe have real experience building complex systems at scale.

I think it only takes an hour or so to become familiar with the structure. I can tell during the interview if that's the problem and I will be very patient in explaining what I'm looking for in that sense.

What is the difference between real experience and books in your opinion? How similar does the experience need to be to the problem at hand for it to be relevant?

I can't say about other companies but I have personally done many, many of these interviews over the years and can say with 100% confidence that someone who has spent days/weeks/months studying system design interview material but not had any actual experience building such systems in a production setting will get weeded out in the first few minutes.

Now some interview prep might actually help a lot of people, but it will help you better present your existing knowledge, not replace it.

I may be a counter example, but I did very well at system design interviews at both Google and Meta (level L5), with no experience building such systems. As a matter of fact, my resume didn't mention any such things and everybody was aware I didn't have that experience - recruiters, interviewers. A lot of candidates don't have that background (there are lot of things to do in our field besides building Twitter newsfeed and Google search autocomplete), and companies don't want to exclude them.

Also, you can build knowledge during your preparation. It's not only about "faking" it.