Andrew Leith focused on backend development and testing for the cds-snc/notification-admin repository, addressing a critical issue in the dashboard’s Redis today-data validation logic. He updated the system to ensure the database is only queried when Redis lacks data for the current day, preventing unnecessary queries that previously occurred when Redis returned zeroed dictionaries. This Python-based solution improved data integrity and reduced database load, resulting in faster and more reliable dashboard metrics. Andrew also revised unit tests to align with the new validation approach, demonstrating careful attention to both code correctness and system performance through targeted API integration and backend enhancements.