My startup currently does just this 'at scale', which is for us ~150 b2b customers with a total database footprint of ~500 GB. We are using Rails and the Apartment gem to do mutli-tenancy via unique databases per account with a single master database holding some top-level tables.
This architecture decisions is one of my biggest regrets, and we are currently in the process of rebuilding into a single database model.
FWIW, this process has worked well for what it was originally intended to do. Data-security has a nice db level stopgap and we can keep customer data nicely isolated. It's nice for extracting all data from a single customer if we have extended debugging work or unique data modeling work. It saves a lot of application layer logic and code. I'm sure for the most part it makes the system slightly faster.
However as we have grown this has become a huge headache. It is blocking major feature refactors and improvements. It restricts our data flexibility a lot. Operationally there are some killers. Data migrations take a long time, and if they fail you are left with multiple databases in different states and no clear sense of where the break occurred.
Lastly, if you use the Apartment gem, you are at the mercy of a poorly supported library that has deep ties into ActiveRecord. The company behind it abandoned this approach as described here: https://influitive.io/our-multi-tenancy-journey-with-postgre...
Happy to expand on this if anybody is interested. It's currently a cause of major frustration in my life.
This architecture decisions is one of my biggest regrets, and we are currently in the process of rebuilding into a single database model.
FWIW, this process has worked well for what it was originally intended to do. Data-security has a nice db level stopgap and we can keep customer data nicely isolated. It's nice for extracting all data from a single customer if we have extended debugging work or unique data modeling work. It saves a lot of application layer logic and code. I'm sure for the most part it makes the system slightly faster.
However as we have grown this has become a huge headache. It is blocking major feature refactors and improvements. It restricts our data flexibility a lot. Operationally there are some killers. Data migrations take a long time, and if they fail you are left with multiple databases in different states and no clear sense of where the break occurred.
Lastly, if you use the Apartment gem, you are at the mercy of a poorly supported library that has deep ties into ActiveRecord. The company behind it abandoned this approach as described here: https://influitive.io/our-multi-tenancy-journey-with-postgre...
Happy to expand on this if anybody is interested. It's currently a cause of major frustration in my life.