This article highlights the limitations and risks associated with using multi-tenant SaaS for authentication. It argues that relying on a cloud-based authentication service can lead to significant security vulnerabilities, data residency issues, and a lack of control over configuration and upgrades. The author emphasizes that modern development workflows require flexibility, speed, and reliability, which multi-tenant SaaS often fails to deliver. Additionally, the article discusses the challenges of testing and debugging authentication systems in a cloud-based environment, as well as the impact on developer productivity. It concludes by stating that organizations should consider alternative solutions that provide more control over their authentication infrastructure.