Worked on Apache Druid to enhance backend reliability and configurability, focusing on percentile analytics and protobuf descriptor management. Developed a null-safe percentile calculation for SpectatorHistogram, ensuring that null inputs yield null percentiles rather than errors, which improved error handling and system stability. Later, implemented dynamic protobuf descriptor loading from both file paths and URLs, addressing a previous regression and strengthening error reporting for malformed URLs. Added comprehensive unit tests to validate these enhancements. The work leveraged Java and backend development skills, emphasizing robust error handling and test coverage to reduce operational friction and support more flexible client configurations.