I was contacted by a Google recruiter over LinkedIn. He then proceeded to schedule a phone interview, which was a month later as I knew it would be tough.

The interviewer was knowledgeable but had a heavy Chinese accent. He asked me about my background and what I would like to do at Google. When I said I would like to work in applications like Gmail, Earth, or YouTube, he asked why not in infrastructure or DevOps.

He then proceeded to give an algorithmic question (over Google Docs) for finding the local minimum value in an array. Although I wrote the correct algorithm in Java with time complexity O(n), he then proceeded to give me hints to optimize it. Here I was found wanting and thus did not receive an offer.

What types of queries or use cases would a column-oriented database be most useful for?