ABSTRACT
As a promising technology, blockchain has found widespread application in numerous decentralized systems. However, the scalability problem of blockchain has drawn considerable criticism. Sharding, an effective technology, offers a solution to enhance blockchain scalability by enabling parallel validation and confirmation of transactions or new block generation. Although extensive research has been conducted on sharding, the existing literature still lacks a thorough review on its current state of arts with comprehensive analysis and evaluation. In this paper, we propose a series of evaluation criteria regarding scalability, applicability, and reliability. Additionally, we classify the cutting-edge sharding schemes based on blockchain type and sharding techniques. We then provide a comprehensive overview of these existing schemes by analyzing their respective advantages and disadvantages according to the proposed criteria. At the end of the survey, we highlight open issues and suggest future research directions based on the results of our meticulous analysis.