Adron Hall looks at multi-tenancy within Postgres:
Music has always been a significant part of my life. From the melodies that accompany my daily routines to the anthems of my most memorable moments, it’s been a constant. As my collection grew, I realized I needed a better way to organize it. That’s when I stumbled upon the concept of multi-tenancy databases and decided to give it a shot with PostgreSQL. Here’s my experience.
Multi-tenancy is one case in which I’m much more relaxed about including the tenant ID on tables where it is not absolutely necessary in order to prevent a series of joins to get the appropriate tenant ID. We can quibble about whether that’s reasonable denormalization or appropriate use of a superkey—especially because, in SQL Server, tenant ID ends up being part of the clustered index and likely part of the primary key anyhow—but it’s extremely useful nonetheless.