Tmark Wu contributed to the opensearch-project/k-NN and opensearch-build repositories by developing features that enhance KNN query flexibility and testing reliability. He implemented direct field name support in KNNQueryBuilder, improving API design and query expressiveness, and introduced validation logic to prevent misconfiguration of vector fields, ensuring data integrity for new indices. In the opensearch-build repository, he expanded KNN testing configuration for OpenSearch 2.20.0 and 3.0.0-alpha1, enabling more robust test coverage. His work leveraged Java, YAML, and configuration management skills, demonstrating a thoughtful approach to backend development, error handling, and maintaining high standards for code safety and maintainability.