“…In order to guarantee quality and highly available services, these services are generally operated on top of multiple datacenters dispersed in different cities or countries close to regional users [1], [2], [3]. Given such architecture, it is necessary to replicate data, such as updated machine learning models and multimedia, across the datacenters that offer the same services to reduce the response latency to access services, enhance failure recovery, and expedite geo-distributed data analytics [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]. A representative example is the search service, where the search engines periodically synchronize their search index databases across multiple locations to improve overall search quality (e.g., relevance and precision) and user satisfaction [9], [10].…”