Megastore: Providing Scalable, Highly Available Storage for Interactive Services

TLDR

Megastore is a storage system designed to meet the needs of interactive online services, blending NoSQL scalability with RDBMS convenience while delivering strong consistency and high availability. The paper describes Megastore’s semantics and replication algorithm. Megastore achieves fully serializable ACID semantics by partitioning data into fine‑grained shards, synchronously replicating writes across datacenters with low latency, and enabling seamless failover. The authors report successful deployment of Megastore across many Google production services.

Abstract

Megastore is a storage system developed to meet the requirements of today’s interactive online services. Megastore blends the scalability of a NoSQL datastore with the convenience of a traditional RDBMS in a novel way, and provides both strong consistency guarantees and high availability. We provide fully serializable ACID semantics within ne-grained partitions of data. This partitioning allows us to synchronously replicate each write across a wide area network with reasonable latency and support seamless failover between datacenters. This paper describes Megastore’s semantics and replication algorithm. It also describes our experience supporting a wide range of Google production services built with Megastore.