JiangZiya: Dependency-aware Smart Contract Migration for Scalable Sharded Blockchains

Sharded blockchains enhance scalability by partitioning the system into parallel shards. However, even with parallel processing, the substantial coordination overhead and suboptimal placement of interdependent contracts lead to significant performance degradation when executing cross-shard transactions (CSTxs). Therefore, efficiently managing costly CSTxs through a dependency-aware placement strategy presents a significant challenge. In this paper, we propose JiangZiya, a dependency-aware smart contract migration mechanism that improves CSTx execution efficiency. We model contract dependencies as a gas-weighted invocation graph to reflect realistic execution costs. Furthermore, we employ a genetic algorithm to optimize contract placement and a dual-mode protocol to execute remaining CSTxs, complemented by a lightweight storage module. Finally, we conduct extensive experiments to compare our work with state-of-the-art baselines on real-world workloads. The evaluation results show that JiangZiya improves throughput by up to 4.2× and reduces latency by up to 74%.