In the past I’ve written about monitoring identity columns to ensure there’s room to grow.
But there’s a related danger that’s a little more subtle. Say you have a table whose identity column is an 8-byte bigint. An application that converts those values to a 4-byte integer will not always fail! Those applications will only fail if the value is larger than 2,147,483,647.
This post specifically pertains to identity columns but don’t forget those non-identity columns when testing.