In this paper we will present the digital library system developed in the framework of the VD17 Project, in which all prints of the 17^th Century published in the Germanspeaking area are being cataloged and partially digitized. The intensive use of this system showed that the current architecture suffers from performance problems. Therefore, scalability is of great importance, and in particular the question arises, in which way and through which measures efficiency can be increased. We will describe some principles, which can generally lead to an increase in performance. Subsequently, we will present our scalable system architecture which improves the performance drastically and allows additional partners to join this project.