Crowdsourcing has gained much attention in practice over the last years. Numerous companies have drawn on this concept for performing different tasks and value creation activities. Nevertheless, despite its popularity, there is still comparatively little well-founded knowledge on crowdsourcing, particularly with regard to crowdsourcing intermediaries. Crowdsourcing intermediaries play a key role in crowdsourcing initiatives as they assure the connection between the crowdsourcing companies and the crowd. However, the issue of how crowdsourcing intermediaries manage crowdsourcing initiatives and the associated challenges has not been addresses by research yet. We address these issues by conducting a case study with a German start-up crowdsourcing intermediary called testCloud that offers software testing services for companies intending to partly or fully outsource their testing activities to a certain crowd. The case study shows that testCloud faces three main challenges, these are: managing the process, managing the crowd and managing the technology. For each dimension, we outline mechanisms that testCloud applies for facing the challenges associated with crowdsourcing projects.