I understand that [post ID's are unique](https://wordpress.stackexchange.com/questions/130232/are-all-ids-used-unique), but are they *reliable* as persistent data ID's?

More specifically, is there a guarantee that, through a migration or another data exchange, post ID's will not change?

I understand wordpress is primarily implemented using MySQL, so ID's are governed by the `AUTO_INCREMENT` mechanism; however, is there any caveat on Wordpress' end that would change this behavior in the future, or potentially with another persistence implementation (such as MongoDB)?