The bottleneck architecture for modern organizations centralizes user management with a single system, routing all authentication and authorization requests through it. This approach enables single sign-on (SSO), increased visibility, decreased operational complexity, and increased choice of authentication methods. The centralized auth system can be configured to delegate decisions to relying parties or service providers, which can federate with external identity providers such as Google, HYPR, or Facebook. A well-maintained user management system accelerates custom application development by providing commonly used services, while making it easy to turn accounts on and off, and offering a better user experience through integration with various third-party accounts. However, there are challenges with this approach, including the SSO tax, ensuring adoption among developers and end-users, tying together the bottleneck system, and selecting a robust and flexible auth service.