The paper aims to examine how users come into play in developing a digital business platform. User involvement in a successful Swedish digital transaction platform serving buyers and sellers of secondhand items is investigated using interviews and observations. The study contributes to user involvement literature and the emergent literature on digital platforms as socio-technical systems by showing how digital platforms attend to what we refer to as active and passive user involvement. The findings highlight the importance of investing in personal user relationships and spending significant time and effort to learn from data collected through several tools and sources. The paper also questions the traditional product development process and its emphasis on front-loading. It discusses back-loading, i.e., time and effort spent postlaunch, as an alternative approach to meet the platform's need for agility and speed and continuous improvement and updates.