Worked on the Velox core repository to address correctness and reliability in SQL join operations, focusing on a critical bug fix for MergeJoin logic involving two join keys and NULL values. Applied C++ programming and SQL expertise to ensure join semantics aligned with SQL standards, reducing incorrect results in edge cases and improving data integrity for analytics users. Collaborated through code reviews and validated the solution with targeted unit and integration tests, documenting the approach for maintainers. This work strengthened the foundation for future performance improvements and demonstrated a methodical approach to debugging and maintaining complex database management systems.