Sebastian developed a domain-based design configuration system for the is-a-dev/register repository, focusing on scalable management of design elements and point-to-point settings. He reorganized and migrated JSON configuration files into a domains/ namespace, introducing domain-scoped variants and integrating DKIM domain key configuration to support email authentication. His approach emphasized configuration management and maintainability, reducing configuration drift and streamlining the onboarding of new domains. By leveraging JSON and Git for structured refactoring, Sebastian improved deployment reliability and positioned the project for enhanced email security. The work demonstrated depth in configuration management, DKIM configuration, and domain-centric design within a production codebase.