Neptune: Scalable Replication Management and Programming Support for Cluster-based Network Services Kai Shen, Tao Yang, Lingkun Chu, JoAnne L. Holliday, Douglas A. Kuschner, and Huican Zhu Department of Computer Science University of California at Santa Barbara Previous research has addressed the scalability and availability issues associated with the construction of cluster-based network services. This paper studies the clustering of replicated services when the persistent service data is frequently updated. To this end we propose Neptune, an infrastructural middleware that provides a flexible interface to aggregate and replicate existing service modules. Neptune accommodates a variety of underlying storage mechanisms, maintains dynamic and location-transparent service mapping to isolate faulty modules and enforce replica consistency. Furthermore, it allows efficient use of a multi-level replica consistency model with staleness control at its highest level. This paper describes Neptune's overall architecture, data replication support, and the results of our performance evaluation.