During January 2025, Tosong worked on backend development for the apache/pinot repository, focusing on improving error handling and exception management. Tosong refactored the system’s query processing logic in Java to ensure that BadQueryRequestException instances are consistently mapped to QueryException.QUERY_VALIDATION_ERROR. This change standardized query validation error reporting across the Pinot platform, resulting in clearer error messages and more reliable error metrics for users and maintainers. The work demonstrated a strong understanding of exception management and backend systems, addressing a specific bug rather than adding new features, and contributed to the maintainability and clarity of Pinot’s query validation process.