Worked on backend reliability improvements for the traP-jp/traO-Judge-judge repository, focusing on user session handling. Addressed a critical bug by aligning the session_id type in the get_user function with the cookie-derived value, changing it to Option<&str> to ensure accurate session validation during user retrieval. This adjustment reduced potential errors in session state and improved the reliability of user information access. Maintained overall codebase stability by delivering a targeted fix without introducing new features. Utilized Rust for backend and API development, demonstrating attention to type safety and robust session management in a production environment over the course of the month.