> You can't add constraint which conflict with old data, yet you need to check that constraint for current data, If there was a way to distinguish "old" and "n

> You can't add constraint which conflict with old data, yet you need to check that constraint for current data, If there was a way to distinguish "old" and "new" data, you could write your constraint to honor the difference. > therefore you must implement those constraints somewhere else and if you have those constraints there anyway, why bother with additional ones. IMHO, if you must only have one set of constraints, put it in the data store. The thing about constraints is that they provide pretty solid guarantees that let you better reason about the data at its base level. You can't reason well about data that was "checked" by dozens of different versions of validations over time. What you have in that case is garbage in need of cleanup.