> One of my data models use natural keys that can change overtime. How are foreign keys and cascades implemented in the latest version of Firebird? Is it like in a REAL rdbms where the foreign key is actually a internal pointer to the referenced table and cascades are "instant" no matter how big the database

Could you point us to the documentation to the such "REAL rdbms" where your statement is confirmed ?

Regards,
Vlad