I've set up systems where I chose 32bit int because I could've never imagined to need more than 4 billion values. AT some points I did (related to deletes) but

I've set up systems where I chose 32bit int because I could've never imagined to need more than 4 billion values. AT some points I did (related to deletes) but changing the datatype when you have >1bn records can be next to impossible for 24/7 operations, especially for primary keys.