Sebastien Bretteville focused on backend development for the glpi-project/glpi repository, where he addressed a critical issue in the certificate expiration alert system. Using PHP and SQL, Sebastien corrected the date calculation logic that determines when certificate expiration alerts are triggered, ensuring users receive accurate and timely notifications. He also resolved an error path in the certificate management workflow that previously led to failures during alert generation. By validating and refining the alert workflow, Sebastien improved the reliability of notifications and reduced the risk of missed or incorrect alerts. His work enhanced operational stability, though it was limited to bug fixing.