As long as I live, I will never forget the interview I had with a guy who asked why I was using a relational database instead of "something NoSQL, like Mongo", and then later, asked what I would do if retrieving n rows turned out to be slow, for reasons, then when I suggested we could saving off the data we cared about as another column in the table, and do a bit of basic arithmetic to recalculate the newer value that we'd care about for the next call, he asked: "Why not just cache the n rows?"
After recovering from the stagger this question caused me, I said, "Well, because then you'd trade one database issue for about a dozen cache query issues." This was at the end of the hour I had with him, and he asked if I had any questions for him as our time was wrapping up, so I fired off: "What's the toughest bug you had to track down within a cache?" He replied, "Actually, I haven't ever done much work with caches..."
I didn't get that job. It was a company that does tech in medical care. It's fine. I'm sure doctors can continue to get work done when their unjournaled medical records suddenly vanish, and when cache refreshes don't trigger as necessary. Diabetes probably isn't a very time-sensitive illness.
When interviewer asks you "why not", it doesn't mean something better. They just want to know how you respond, how you prove your point, how far you know about that knowledge, and the ability to analyze the problem.
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As long as I live, I will never forget the interview I had with a guy who asked why I was using a relational database instead of "something NoSQL, like Mongo", and then later, asked what I would do if retrieving
nrows turned out to be slow, for reasons, then when I suggested we could saving off the data we cared about as another column in the table, and do a bit of basic arithmetic to recalculate the newer value that we'd care about for the next call, he asked: "Why not just cache thenrows?"After recovering from the stagger this question caused me, I said, "Well, because then you'd trade one database issue for about a dozen cache query issues." This was at the end of the hour I had with him, and he asked if I had any questions for him as our time was wrapping up, so I fired off: "What's the toughest bug you had to track down within a cache?" He replied, "Actually, I haven't ever done much work with caches..."
I didn't get that job. It was a company that does tech in medical care. It's fine. I'm sure doctors can continue to get work done when their unjournaled medical records suddenly vanish, and when cache refreshes don't trigger as necessary. Diabetes probably isn't a very time-sensitive illness.
When interviewer asks you "why not", it doesn't mean something better. They just want to know how you respond, how you prove your point, how far you know about that knowledge, and the ability to analyze the problem.