Making LSM-Tree-based Key-Value Store Practical and Efficient for Multi-Tenant Serverless Cloud Databases

Cloud databases revolutionize data processing and storage by providing on-demand and scalable services housed on the cloud infrastructure. Multi-tenancy and serverless are two key tenets transforming the cloud database architecture, offering significant cost savings and simplified user management. However, we found that cloud databases using LSM-tree-based key-value stores as the storage engine face a crucial conundrum when adopting this promising multi-tenant serverless architecture. Specifically, LSM-tree-based key-value store encounters a critical dilemma between maintaining performance service-level agreements (SLAs) for tenants and over-subscribing storage bandwidth for high cost-efficiency. In this paper, we present FlexEngine, a novel LSM-tree-based key-value store, which for the first time enables the practical and efficient adoption of LSM tree in multi-tenant serverless cloud databases. FlexEngine introduces a series of designs to navigate the above dilemma, including a two-level (i.e., partition- and node-level) I/O admission control framework and a two-stage compaction deferral mechanism. We implement FlexEngine on a commercially-deployed RocksDB and perform comprehensive experiments on both production traces and micro-level workloads. The experimental results demonstrate that FlexEngine can significantly improve the capability to over-subscribe storage bandwidth, which leads to high cost-efficiency, while still promising consistent performance SLAs for users.