Cryptology ePrint Archive: Report 2020/1466

Load Balancing for Sharded Blockchains

Naoya Okanami and Ryuya Nakamura and Takashi Nishide

Abstract: Sharding is an approach to designing a highly scalable blockchain. A sharded blockchain achieves parallelism by dividing consensus nodes (validators) into groups called shards and making them process different transactions in each shard. In this paper, we economically analyze usersí behavior on sharded blockchains and identify a phenomenon that usersí accounts and smart contracts eventually get concentrated in a few shards, making shard loads unfair. This phenomenon leads to bad user experiences, such as delays in transaction inclusions and increased transaction fees. To solve the above problem, we propose a load balancing framework in sharded blockchains in which accounts and contracts are frequently reassigned into shards to reduce the difference of loads between shards. We formulate the contract reassignment as an optimization problem and present the algorithm to solve it. Further, we apply the framework to an existing sharding design (Ethereum 2.0) and modify the protocol to do load balancing. Finally, we simulate the protocol and observe smaller transaction delays and fees.

Category / Keywords: applications / Sharding, Blockchain, Load balancing, Game theory, Heuristics, Simulated annealing.

Original Publication (with minor differences): International Conference on Financial Cryptography and Data Security

Date: received 20 Nov 2020, last revised 21 Dec 2020

Contact author: naoya okanami at layerx co jp,ryuya nakamura@layerx co jp

Available format(s): PDF | BibTeX Citation

Version: 20201221:091012 (All versions of this report)

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