I'm not sure why you want a uniqueness index then in this case. If it's not publicly visible (effectively a secondary index / reference), then you can't use it

I'm not sure why you want a uniqueness index then in this case. If it's not publicly visible (effectively a secondary index / reference), then you can't use it as an identifier. This means you need something else (a slug, as discussed herein) or just use the ID (bad practice in general) or UUID (bad for humans). If you use - in this example - city and company name - you still have to enforce uniqueness, so you have a pseudo-slug anyway.