Andrey Marchenko focused on stabilizing the CI queue subsystem in the Shopify/ci-queue repository, addressing a crash that occurred when acknowledging records in static queues. He enhanced the backend Ruby codebase by introducing a new parameter to the record_success method, enabling more accurate tracking of static queue successes. Andrey applied test-driven development practices to add targeted automated tests, ensuring the fix would prevent future regressions. His work improved the reliability and robustness of continuous integration workflows, reducing potential pipeline interruptions for the team. Throughout the project, he demonstrated backend development and testing skills, emphasizing maintainability and peer-reviewed code quality.