Schema design tends to be a bit different than in a traditional relational database due to the different constraints and capabilities. For instance, IIRC Faceb

Schema design tends to be a bit different than in a traditional relational database due to the different constraints and capabilities. For instance, IIRC Facebook has a video talking about how they use HBase for messages, and they have an example of a table indexing the messages for search: Each row contains the index of one user. For each word in a message they insert an entry in the row with the word as the column name, the message id as the version (a column can have several values with different versions), and maybe some additional info in the value. You can see how you'd quickly reach a million columns when every word in every message you send or receive becomes a column entry. It may have been this presentation: http://www.infoq.com/presentations/HBase-at-Facebook/ http://www.infoq.com/presentations/HBase-at-Facebook/