>> By "interesting cases" I mean applications that leverage the more unique features in different database systems Actually, most ORMs like Hibernate allow you

>> By "interesting cases" I mean applications that leverage the more unique features in different database systems Actually, most ORMs like Hibernate allow you to write native SQL (or even stored procedure) to take advantage of native db features. In that case, you have to trade-off portability, if that feature is important to you. >> or more serious differences related e.g. to locking (so an application that works fine on one database fails spectacularly on another one) Locking (default - READ_COMMITTED) also works consistently across databases. The problem happens only when you introduce distributed ORM cache where data is not updated synchronously across the cluster. It is a reasonable trade-off for performance.