Andrei Serdan focused on enhancing data integrity within the Stefan2114/UBB-SE-2025-927-2 repository by implementing a cascade cleanup mechanism for group deletions. Leveraging SQL and schema design expertise, he introduced automated removal of related records such as posts, reactions, comments, and group memberships when a group is deleted, effectively preventing orphaned data and reducing the need for manual intervention. Andrei also designed and integrated a new meal_types table to standardize meal-type data across the application. His work demonstrated a solid understanding of database management principles, with a targeted approach to schema evolution and enforcement of referential integrity.