Worked on the frappe/frappe repository to enhance the database query engine’s handling of permission checks, focusing on aligning access control with parent-child table relationships while excluding Single DocTypes. Addressed a critical bug by correcting the join logic in permission-related queries, ensuring that permission conditions referencing parent tables are accurately enforced for child tables. This backend development effort, implemented in Python and leveraging advanced SQL joins and ORM debugging, improved the reliability and security of data access across the system. The work also involved thorough testing, regression planning, and collaborative code review, contributing to more robust database management and compliance.