2 min read
Building Secure Multi-Tenant SaaS Applications
A practical look at tenant isolation, authorization, data boundaries and the mistakes that can expose customer data.
Clean Architecture can make a growing application easier to maintain, but only when its boundaries solve real problems. Adding layers and interfaces without a clear reason can make development slower instead of safer.
Keep business rules inside the domain
Entities and value objects should protect important invariants instead of acting only as database containers.
Business decisions that do not depend on external systems belong close to the domain model.
Use the application layer for workflows
The application layer coordinates use cases such as creating an invoice, inviting a member or approving a workflow step.
It should depend on abstractions for persistence, email, files and external services.
Keep technical implementations in infrastructure
Entity Framework Core, email providers, storage services and payment integrations belong in infrastructure.
This keeps the business and application layers independent from specific vendors.
Keep controllers thin
Controllers should validate the HTTP boundary, resolve the current user and delegate the use case.
Large controllers often indicate that business logic has leaked into the presentation layer.
Strong software architecture is not about adding the most layers. It is about protecting the boundaries that matter.
Key takeaways
01
Use architecture boundaries to protect real responsibilities.
02
Do not create interfaces only for the sake of having interfaces.
03
Keep controllers focused on HTTP concerns.
04
Let infrastructure depend on the application, not the opposite.
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