Worked on enhancing the robustness and reliability of the authentication stack in the keycloak/keycloak repository, focusing on backend development with Java and comprehensive testing. Addressed a NullPointerException that occurred during login with mixed-case email domains by normalizing domain names to lowercase for Infinispan cache keys, ensuring consistent cache behavior with JPA’s case-insensitive expectations. Introduced defensive null checks to prevent errors from stale cache entries and expanded integration test coverage, including remediation of a flaky test scenario. These improvements reduced production incidents related to login and cache resolution, demonstrating a methodical approach to stability and maintainability in authentication workflows.