Yaroslav focused on enhancing data traceability and migration reliability in the profcomff/rental-api repository during November 2025. He implemented session-based strike tracking by adding a session_id column with a foreign key to the rental_session table, ensuring accurate association of strikes with user sessions. Using Python and pytest, he developed and validated migration tests to guarantee both upgrade and downgrade compatibility, addressing issues in the downgrade path and refining revision history retrieval for precise migration records. His work improved data integrity and reduced deployment risk, demonstrating a thorough approach to database migrations and testing within a production API environment.