Worked on the typeorm/typeorm repository to address a targeted backend issue affecting query cloning reliability. Focused on stabilizing the useIndex property during the cloning of QueryExpressionMap and QueryBuilder, ensuring that query-building behavior remained consistent for developers relying on this feature. Utilized JavaScript and TypeScript to implement the fix, adding regression tests to verify that useIndex persisted correctly after cloning operations. Emphasized code maintainability and long-term stability by integrating thorough test coverage. Demonstrated skills in backend development, database querying, and testing, contributing to the overall robustness and reliability of TypeORM’s query-building and cloning mechanisms.