Previous studies measuring the performance of general-purpose operating systems running large-scale Internet server applications, such as proxy caches, have identified design deficiencies that contribute to lower than expected performance and scalability. This paper introduces a high-capacity proxy cache service built upon a specialized operating system designed to efficiently support largescale Internet middleware. It suggests that specialized operating systems can better meet the needs of these services than can their general-purpose counterparts. It concludes with the measured performance and scalability of this proxy cache service.