LB-Chain: Load-Balanced and Low-Latency Blockchain Sharding via Account Migration

Abstract

Blockchain sharding has been increasingly used to improve blockchain systems’ performance, in which a blockchain is split into multiple smaller, disjoint shards. In practice, however, sharding can only achieve limited throughput and latency improvement, especially for theuser-perceived transaction confirmation delay.The performance degradation is believed to be caused by the cross-shard transactions. However, we show, through comprehensive system deployment and measurement studies, that the main culprit is theimbalanced transaction loadon different blockchain shards. To address this problem, we propose a novel sharding system, called LB-Chain, whichdynamicallybalances the transaction load on different shards by periodicallymigrating active accountsfrom heavily-loaded shards to less-loaded ones. We have implemented a prototype of LB-Chain, and evaluated its performance through large-scale blockchain deployment using real-world transaction traces. Extensive experiments confirm that LB-Chain significantly boosts sharding performance, reducing the transaction confirmation delays by up to 90% while increasing the transaction throughput by more than 10%. The delay difference between different accounts is also reduced dramatically, leading to improved fairness in the system.