1Mio User on a Grafana server - Permission


Lets say a Grafana system should be able to handle 1Mio Dashboards.
For each Dashboard are just 1-2 different users. No User should have access to another dashboard.

What is here the past practices?
To better handle I like to create less organizations.
But could I set, that user in the same organization, has just access to their own dashboard?
Or did I need to set a own organization for each user?

Thank you!