I am building my 3rd multitenant SAAS solution. I am not referencing any of my earlier work because I think they were way more work than they should have been. Also, I have since moved on from the whole ASP.net web forms development mindset and I want to start with a fresh perspective instead of trying to improve my big balls of spaghetti code.

Today, my thoughts center around enforcing the inclusion and processing of a tenant ID in every command and query. My tenant model keeps all tenant data in a shared database and tables. To keep everything segregated every time I write data and read data there has to be a tenant ID included so that we don’t mess with the wrong tenants data.

I have seen all kinds of solutions for this, some more complicating than I care to tackle at this moment. I am currently leaning towards enforcing it in the data repository.

I am using a generic repository for CRUD operations and an event repository for async event driven workflows. In the repository API’s I want to introduce a validated parameter for tenant ID in every write and read operation. This will force all clients to provide the ID when they call the repos.

I just have to update a couple classes in the repos to enforce inclusion of the tenant ID when I write data. Also, every read will use the tenant ID to scope the result set to a specific tenant’s data. I already have a proof of concept for this app so this change will cause a breaking change in my existing clients, but still not a lot of work considering the fact that I almost decided to enforce the tenant ID in a layer higher than the repo, which would have been a maintenance nightmare.

Is this best practice? No. I don’t think there is a best practice besides the fact that you should use a tenant ID to segregate tenant data in a shared data store. This solution works for my problem and I am able to maintain it in just a couple classes. If the problem changes I can look into the fancy solutions I read about.

Now, how will I resolve the tenant ID? Sub-folder, sub-domain, query string, custom domain…?