Using email as internal ID... Where? Emails would change. Same with phone numbers. I've never seen it, it is usually lives in a column in the table and is use

Using email as internal ID... Where? Emails would change. Same with phone numbers. I've never seen it, it is usually lives in a column in the table and is used to login. But internal ids are UUIDs or integers in the relational DB. I've seen people use phone number as an ID, but it is bad for GDPR and privacy reasons... I've seen people use incrementing ID and expose it to the user inside URLs (leaking the account registration time and the total number of users).