Scalable Join Queries in Cloud Data Stores

Cloud data stores provide scalability and high availability properties for Web applications, but do not support complex queries such as joins. Web application developers must therefore design their programs according to the peculiarities of No SQL data stores rather than established software engineering practice. This results in complex and error-prone code, especially with respect to subtle issues such as data consistency under concurrent read/write queries. We present join query support in Cloud TPS, a middleware layer which stands between a Web application and its data store. The system enforces strong data consistency and scales linearly under a demanding workload composed of join queries and read-write transactions. In large-scale deployments, Cloud TPS outperforms replicated Postgre SQL up to three times.