Case-sensitive user-restricted data access

Hi everyone,

my app uses a shared index with personal user data. I was following the User-restricted access to data guide to restrict each user’s access to their own records. As far as I understand, filtering is case-insensitive.

Sadly, my userIDs are case-sensitive strings. Is there a way to make the filtering case-sensitive or a suggested way to restrict access by case-sensitive strings?

Kind Regards