SconeKV: A Scalable, Strongly Consistent Key-Value Store

For decades, relational databases provided a strong foundation for constructing applications due to their ACID properties. However, distributed applications reached a scale, both in terms of data volume and number of concurrent clients, that traditional databases cannot accommodate. NoSQL databases addressed this problem by trading consistency for scalability, namely through horizontal scalability schemes supported by optimistic replication protocols, which only guarantee eventual consistency. In this paper, we explore a novel design between the two extremes, which is able to scale to large deployments while still offering strong consistency guarantees in the form of serializable transactions. Our key insight is to leverage recent advances in membership services that provide strongly consistent views at scale. Those assurances from the membership layer simplify building efficient and consistent storage protocols. Our evaluation of the resulting system, SconeKV, in a realistic scenario shows that it scales and performs better than CockroachDB while being competitive with Cassandra.