I'm still not sure what fortress actually does that is new.

What I'm guessing is that if you have a isolation=shared tenant you add a database to an existing postgresql cluster and if it is set to isolation=dedicated you setup a separate cluster? The clusters are setup with normal postgresql hosted solutions like AWS aurora and billed in the same way, right?

If so I don't understand why I'd use your product over any traditional IaC like CDK or terraform where I have done similar stuff (spin up multiple instances/clusters/databases based on tenants) and seems to integrate better with existing devops tooling or a workflow on top of CDK/terraform scripts that creates databases/schemas.