Well, NoSQL databases is a pretty broad term. Not all NoSQL databases are created alike, for example, MongoDB is a "document orientated database" where as HBase

Well, NoSQL databases is a pretty broad term. Not all NoSQL databases are created alike, for example, MongoDB is a "document orientated database" where as HBase is a "column-oriented store" based on the Google BigTable whitepaper. As far as I know, key design is not an important aspect with MongoDB but I could be mistaken. HBase has a pretty awesome book (http://www.hbasebook.com/ http://www.hbasebook.com/), which has an entire chapter dedicated to key design. Lars (the author) also has a pretty in depth 1 hour video on key design (http://www.youtube.com/watch?v=_HLoH_PgrLk http://www.youtube.com/watch?v=_HLoH_PgrLk). HBase is pretty widely used, I've seen 1200+ node clusters running production tables.