Postgres is quite different in one respect: it has a truly serializable snapshot isolation, at an acceptable performance cost (single digit percentage generally

Postgres is quite different in one respect: it has a truly serializable snapshot isolation, at an acceptable performance cost (single digit percentage generally). Other DB systems are either not truly serializable, or have lock-based systems that are sometimes more difficult to work with for web apps. > 'applications using this level must be prepared to retry transactions due to serialization failures' True of any serializable system that supports concurrent access, AFAIK - not quite sure that's a fair criticism :-). ------ > And, typically, transactions between tables or even rows are difficult/impossible for a distributed database Depends what you mean by 'distributed', really - Oracle RAC is very much distributed, and supports normal transactional behaviour. On the other hand you won't get that working across a large geographical area. I accept that understanding the impact of isolation levels can be complex - I'm just very much of the opinion that you'll take a lot more pain trying to maintain consistency in a typical NoSQL system.