SuperTokens is an open source authentication solution offering features like: Different types of login: Email / password, Passwordless (OTP or Magic link based).

SuperTokens.com

Question, should I use the same db instance for the entire project or is it better practice to have a dedicated database for supertokens?

You can use the same db instance, but just crests a different db in it.

But even just putting it all in your existing db with some prefix to the table names is fine.

May i know what should be the recommended way?

I’d put it in the same db with a prefix to all the table names

Could you please explain the pros/cons of that solution?

I’m not really sure at the moment. Just a personal choice.