Disagree on this one. In an interview there is no "the answer", it's a dialogue. I've interviewed a lot of people, often using performance related questions, and trust me, there are lots of candidates whose only answer to those is "add a cache", even after multiple follow-up questions or hints like "is there anything else that can be done?", "try thinking outside the box", "what can be done with the database itself", etc. Only a novice interviewer will be fooled by the first answer. If you cannot demonstrate more solutions after that, it shows that you clearly have no experience or problem-solving ability, which is the whole point of the interview to find out, not whether you have studied through a set of common questions.
btw, "scale up" is the second most common answer from those who can't provide better solutions. :)
> and trust me, there are lots of candidates whose only answer to those is "add a cache", even after multiple follow-up questions or hints
My point isn't that the interview can't weed out bad candidates. That's in a way the easy part. The problem is it can't identify not-bad candidates.
The interview is broken because of how standardized it is. It's like a certain game genre and most people will play it the same way. It's more like a memory test.
> In an interview there is no "the answer", it's a dialogue.
It pretends to be or you assume it is. There are numerous 'tutorials' / videos / guides on system design it's >90% rehearsed. So again, my point is the interviewee is trained and will give you the standard answer even if you deviate some. There are just too many risks otherwise. If I had a more novel approach I'd risk the interviewer not understanding or taking longer than the allocated time to finish.
Especially in big tech - interviewers are trained to look for "signals" and not whether you're good or bad. They need to tick certain boxes. Even if you have a "better" answer if it's outside the box it fails.
btw, "scale up" is the second most common answer from those who can't provide better solutions. :)