Hayao focused on stabilizing DataBrew-related test suites within the localstack/moto repository, addressing reliability issues in AWS Glue workflows. He implemented UTC-aware timestamp handling in Python-based tests to resolve timezone-related flakiness, ensuring consistent validation across environments. By developing new end-to-end tests for recipe creation and publishing, including support for descriptions and tags, Hayao expanded coverage of core DataBrew functionality. His backend development and testing efforts enhanced the maintainability of DataBrew and Glue components, reducing the likelihood of regressions. The work demonstrated a methodical approach to improving service reliability through targeted test enhancements and careful attention to edge-case handling.