[sandeepkd]

For the sake of discussion lets leave the business aspect. What you are offering is a service for managed database, similar to lot of cloud providers. What you have on the top of it is a OAuth2 process to obtain relevant credentials.

From practical standpoint you have to consider that the traditional use case for databases has been N:1 (n application instances, 1 DB) and you are inverting this.

There might be some unique B2C scenario where this makes business sense, however if you are providing database service then I cannot see how this would be any different.

On a side note, there are quite a number of B2B scenario where the client provides the DB for data residency requirements and the service providers uses that DB to manage the data on behalf of the client.

The price is also a big concern, a user scope database is going to be quite costly, as a provider you would end up sharing the infrastructure

Lastly I will repeat it again, schema migrations are as much as database level concern, and migrating N databases above a certain scale is not easy.