Michal Charemza focused on stabilizing the API surface for the uktrade/redbox repository, addressing backend reliability through targeted bug fixes. He improved API test reliability by refining error handling expectations and removing deprecated fields, specifically eliminating the use of the date_joined attribute to simplify API contracts. Using Django and Python, Michal verified and strengthened API key authentication across selected endpoints, ensuring that access flows and error messages aligned with consumer expectations. His work in API testing reduced test flakiness and established a more predictable baseline for user views and forbidden access scenarios, laying groundwork for future backend enhancements and maintainability.