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I would imagine that for a certain number of candidates, they answer with a custom solution because they believe this is what the interviewer is expecting to he

I would imagine that for a certain number of candidates, they answer with a custom solution because they believe this is what the interviewer is expecting to hear (and asking for) when the question contains "you need to design, build, and deploy...". I think to some people, the immediate thought is that the interviewer would deduct points for originality if you said "well let's just use this tool off of the shelf". This is why interviews are so tricky - it's hard as a candidate to juggle answering the question and trying to decipher what traits the interviewer is really trying to expose with this question. For example with this one: is the interviewer trying to see if I understand my data structures and the size of this data to the point where I could design such a system from the ground up? Or are they trying to see how practical I can be given real-world time constraints?

brianm 16y ago
I agree, and I try to make clear that I really want to understand how the candidate would approach it -- if they genuinely would try to find a perfect hash and keep a hash -> offset map in memory, then mmap a big data file, that is fine. I will ask how they will find the perfect hash, etc. If you can describe well the approach you take, then this is fine. Ofttimes, though, candidates have started designing a general purpose on-disk hash database. That is fine and dandy, and we always need a better database, but it is pretty orthogonal to the immediate problem. Actually, ofttimes engineers have implemented general purpose on-disk hash databases as part of j. random project, so that path certainly does occur on real projects :-)