Worked on the trinodb/trino repository to address a critical issue in Delta Lake’s write cleanup process, focusing on backend development and testing using Java. Delivered a targeted bug fix that prevents the accidental deletion of active source files during failed write operations, specifically by filtering DataFileInfo entries with a deletionVector when building cleanup lists. This approach preserved data integrity and reduced the risk of data loss or table corruption during transaction conflicts. The work stabilized the DeltaLakeMergeSink write path, with thorough code review and focused testing to ensure reliability and maintain data availability for Delta Lake workloads in production environments.