Johannes Bao refactored the persistence layer for the JointGridContainer in the ie3-institute/PowerSystemDataModel repository, focusing on simplifying and stabilizing data storage processes. He extracted raw grid elements, system participants, and graphic elements using the allEntitiesAsList() method, which reduced verbosity and overall complexity in the persistJointGrid workflow. Working primarily with Java, Johannes applied principles of data modeling, database integration, and object-oriented programming to create a cleaner, more maintainable codebase. This targeted feature work improved the clarity and maintainability of the persistence logic, laying a stronger foundation for future enhancements without introducing new bugs during the development period.