Polyglot Persistence, choosing difference approach for storage - http://martinfowler.com/bliki/PolyglotPersistence.html http://martinfowler.com/articles/nosql-intro.pdf

How leveldb store data? SSTable ( Sorted String Table ) - http://www.igvita.com/2012/02/06/sstable-and-log-structured-storage-leveldb/