>>Just to answer on your 4byte question. Integer is 4 bytes, that's while it's more efficient than other types for PK.
>
>So, I am ok on that one.
>
>But, I am about to reach a limit on the current primary key value. So, I would need to opt that to Big Int I guess. Would that still be valid as far as best usage of primary keys?

Yes. 8 bytes for BigInt.

BTW, don't forget that you can use negative values for Integer key. So, if you only used positive values, there is a possibility to go negative and keep Int.

But if you anticipate you do need to use BigInt, so be it. It would be a pain to change the existing type, though.