Can I host supertokens core and use it like a multi tenancy system?

Can you elaborate on what you want to do please?

I have different domains, with different users base. Can both domain share the same instance of super tokens core?

Not yet. We will be working on multi tenancy soon. But for now, either you can self host multiple cores (connected to different dbs, or different table name prefixes), or sign up and create different accounts on our site.