Toward reducing cross-shard transaction overhead in sharded blockchains

BSTRACTSharding is a promising approach to high-performance blockchains and has been extensively explored in academia recently. However, sharding also introduces cross-shard transactions, which require expensive inter-shard coordination to ensure state consistency. Such transactions significantly limit the performance of sharded blockchains. To reduce cross-shard transactions in UTXO-based sharded blockchains, we propose Rooted Graph Placement, which identifies the most appropriate shard for a transaction based on the interaction between the transaction and historical transactions. In conjunction with the placement algorithm, we also devise two techniques to lessen the system performance impact of the remaining cross-shard transactions. One technique parallelizes dependent transaction verification with the atomic commit protocol, and the other consolidates the atomic commit protocol. Combining all the three techniques, we can improve the maximum system throughput by 118% when compared with a state-of-the-art transaction placement algorithm.