Contributed to the django/django repository by delivering enhancements to the Object-Relational Mapper, specifically targeting composite primary key support. Focused on improving data integrity and performance, the work introduced OuterRef support for composite primary key lookups and added validation to prevent non-local fields in composite keys. Addressed issues in the update path for composite primary keys with default values, ensuring unnecessary writes are avoided, and expanded the test suite to cover edge cases such as falsey default primary keys. Leveraged Python, Django, and database management skills, applying test-driven development practices to strengthen backend reliability and maintainability for complex data models.