Worked on backend reliability and test stability for the wazuh-indexer and questdb repositories, focusing on Java-based integration testing and caching. Addressed flaky Ehcache Disk Cache integration tests in wazuh-indexer by refining cache utilization and introducing robust cache-warming checks, which improved test suite reliability and reduced CI failures. In questdb, targeted the regex replace functionality, resolving stack overflow-related test failures and enhancing error handling for clearer diagnostics and safer recovery. These efforts strengthened core robustness and maintainability, leveraging skills in Java, caching, and regex to ensure more predictable production behavior and smoother onboarding for future stability improvements.