Couchbase Server 7.1 introduces significant improvements to its Rebalance feature, particularly for the Global Secondary Index Service, through a new element called Smart Batching, which optimizes the index redistribution process when nodes are added or removed from a cluster. The Rebalance operation, critical for maintaining balanced resource usage across nodes, occurs in two phases: Planning, where a simulated annealing algorithm determines an efficient index layout, and Movement, where metadata is relocated, and indexes are rebuilt at new nodes. Smart Batching enhances performance by increasing pipeline parallelism, optimizing data stream sharing, and repairing replicas before moving indexes, thereby reducing resource consumption and minimizing impacts on production workloads. Additionally, it supports greater concurrency by allowing larger batch sizes and considers node load to manage concurrency more effectively. These improvements make the Index Service Rebalance more efficient and less disruptive, enabling Couchbase clusters to maintain optimal performance even as they scale or change.