This exploratory paper examines a tension between interacting and documenting as knowledge sharing tasks on Stack Overflow, a platform that supports informal learning at scale in the domain of programming. The study works with platform data in the form of the text of posts and accompanying metadata along with 16 interviews with users. Drawing on trace ethnography as an approach to maintaining an interpretive stance while combining several types of data, this preliminary analysis discusses two interrelated particularities of the tension. The discussion of these particularities, platform mechanics and competing temporalities, helps to unpack a tension that is both a phenomenon of analytic interest and a member’s concern for users of the platform.