During December 2024, Pieter Zandbergen focused on backend development for the Adyen/adyen-magento2 repository, addressing a critical issue in the payment flow. He resolved a bug where multiple orders could exist for a single quote by updating the order retrieval logic to always select the most recent order, using entity ID sorting and result limiting. This change improved checkout reliability and reduced the risk of processing stale orders. Pieter enhanced the unit tests for both the OrderRepository and Sort Order Builder, ensuring robust test coverage. His work demonstrated proficiency in PHP, Magento 2, API integration, and test-driven development practices.