[shariqm]

Clustrix says it provides repeatable-read because it complies with the ANSI spec. In truth we actually provide something closer to snapshot-isolation by default. Snapshot isolation in summary is a guarantee that all reads made in a transaction will see a consistent state of the database. A transaction will only fail to commit if there is a conflict of two updates. This is a strong isolation level that does have a set of anomalies but most companies don't care about them. Microsoft put out a great paper about snapshot-isolation: http://research.microsoft.com/pubs/69541/tr-95-51.pdf

As the post points out, weaker isolation levels allow for more concurrency which translates to more scalability, which is why we chose our isolation level.