When building a new SaaS application, one of the earliest and most consequential decisions is the tenancy model.

The spectrum ranges from fully isolated single-tenant deployments (separate app and database per customer) to fully shared multi-tenant systems with a single database and row-level separation, and several patterns in between.

This choice becomes extremely expensive to change once you have real customer data, so it deserves careful consideration up front.

Microsoft published a solid overview of the main tenancy patterns for Azure SQL, including pros, cons, scalability limits, operational complexity, and cost implications for each approach.

Worth a read if you’re in the architecture phase: https://learn.microsoft.com/en-us/azure/azure-sql/database/saas-tenancy-app-design-patterns?view=azuresql

No universal right answer; it depends entirely on your expected tenant count, isolation requirements, and cost targets.