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I have an upcoming interview for a position at a company that deals with multi-petabyte scale data volumes. They're going to grill me about standard database design questions, but what are the best things to focus my revision/prep work on? How does database design change when you get to really gigantic scales?

I currently think about:

  • Indexes fitting in memory
  • In transactional tables (e.g. ad clickstream) splitting the data up into 1 table per month, or having a "recent" and "historical" set of tables with a flushing job every night or week.
  • Over-normalization - unnecessary primary keys and dimensions (such as a separate table for US zipcodes).

Any suggestions appreciated

  • I'm dealing with terabyte-scale data, so can't talk to the problems that arise at petabyte-scale. But even with the volumes that I'm dealing with, you have to think about physical limitations: just moving a terabyte across a 1Gbit network will take 3 hours, assuming you can saturate the network. Even reading into memory with a 6Gbit SATA takes a long time. I would infer that at petabyte scale, you flow the data into wherever it's going to spend the rest of its life. And of course move processing close to the data. – kdgregory Jun 4 '17 at 14:37
  • Thanks! Network bandwidth is definitely something I should think about. Want to put that as the answer and i'll accept it? – LittleBobbyTables Jun 4 '17 at 18:32
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Try basic database models eg network db model and how to apply them also database relationships using primary keys

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