Michał Pieczyński enhanced the KlubJagiellonski/pola-backend repository by refactoring the get_by_code API response to nest brand details under each company, replacing the previous top-level all_company_brands field. This backend development work, implemented in Python and YAML, focused on improving data organization and reducing client-side parsing complexity. By restructuring the JSON output, Michał laid a foundation for future brand-related features and increased the maintainability of the codebase. The approach demonstrated thoughtful API design and careful refactoring, addressing integration challenges for downstream services and enabling faster, more reliable client consumption without introducing new bugs during the development period.