Sawada, a developer at TIER IV, outlines the company's transition from an in-house IdentityServer infrastructure to the Ory stack, comprised of Ory Kratos, Ory Hydra, and Ory Oathkeeper, to enhance their authentication and authorization systems. The move was prompted by scalability concerns and maintenance issues with their previous OpenID Provider library, which was no longer supported and exhibited performance problems. The new system, implemented in Go rather than Python, offers a microservice architecture that facilitates compatibility during migration, allowing the integration of existing data with minimal disruption. Notably, challenges in migrating identifiers and user passwords were addressed through innovative solutions, such as ID conversion mechanisms and password import capabilities. The decision to adopt Ory was influenced by the team's familiarity with the Go language and past experiences with Ory Hydra, as well as the microservice design that aligns with their modular infrastructure needs. The migration was completed successfully within three months, aided by careful planning and the removal of unnecessary features, along with effective collaboration with business and legal departments to ensure a smooth transition. The open-source nature of the Ory stack provides ongoing opportunities for further enhancements to their identity infrastructure.