Worked on the Sequelize repository to enhance the reliability of upsert operations across multiple SQL dialects. Addressed a core bug by implementing dialect-aware error handling within the query-interface, ensuring that errors are only thrown when a dialect explicitly lacks upsert support. This approach reduced false positives and improved the robustness of cross-dialect applications. Leveraged JavaScript for backend development and database management, aligning upsert logic with each dialect’s capabilities. The targeted fix clarified upsert behavior, making the codebase more maintainable and predictable for developers working with diverse database backends. Delivered these improvements through a clearly documented and traceable commit.