In February 2025, Klenk enhanced the urlaubsverwaltung/urlaubsverwaltung repository by expanding its API to support visibility of inactive users and their activity status. He introduced an active query parameter to the /api/persons endpoint and added an Active flag to the PersonDto data model, enabling downstream systems to distinguish between active and inactive users. This Java Spring Boot backend development preserved default behavior for existing consumers while improving data transparency and integration capabilities. Although the work focused on a single feature and did not address bug fixes, it demonstrated thoughtful API design and careful attention to backward compatibility and reporting needs.