Please excuse my ignorance - how do I enforce nontrivial system-wide invariants with lots of little databases rather than a single consolidated one?<p>The invariants I care about are:<p>(0) Referential integrity. If the table `Foo` has a `FOREIGN KEY (BarID) REFERENCES Bar (BarID)`, then no row in `Foo` must be seen as having a `BarID` whose value can&#x27;t be found in the table `Bar`.<p>(1) Linearizability. There must exist a total order on the entire transaction history of a database, such that, starting from the empty database, and executing the transactions nonconcurrently in the given total order, the result is the current state of the database. (NOTE: The transaction history need not be physically stored anywhere. So this invariant can&#x27;t be “tested” - it has to be proven to hold.)<p>These guarantees are so basic, so fundamental in my everyday use of RDBMSs, that I need to be convinced that they hold.