A Review on Scalability of Blockchain

As one of the key technologies of distributed ledgers, blockchain solves the trust problem in open network without relying on any trusted third party. Its decentralized feature has a broad application prospect, but still faces scalability problem. Currently, blockchain scalability bottleneck is mainly in three aspects: performance inefficiency, high confirmation delay, and function extension. For example, Bitcoin can only deal with 7 transactions per second averagely. Obviously, it cannot meet the requirement of current digital payment scenarios, nor can it be carried in other applications such as distributed storage and credit service. What's more, different blockchain systems carry different business and requirements, so scalability is the core issue of the current development of blockchain. This paper introduces the blockchain scalability related technologies from the aspects of improving efficiency and extending functionality of blockchain system, respectively. We summarize four mainstream solutions to improve the performance of blockchain system, including Sharding mechanism, directed acyclic graph based (DAG-based), off-chain payment network and cross-chain technology. In the end, we give some suggestions for further research in blockchain scalability.