Fast database engines have become an essential building block in many systems and applications. Yet most of them are designed based on on-premise solutions and do not directly work in the cloud. Existing cloud-native database systems are mostly disk resident databases that follow a storage-centric design and exploit the potential of modern cloud infrastructure, such as manycore processors, large main memory and persistent memory. However, in-memory databases are infrequent and untapped.

Database systems are becoming increasingly multi-engine. In particular, a main-memory database engine may coexist with a traditional storage-centric engine in a system to support various applications. It is desirable to allow applications to access data in both engines using cross-engine transactions. But existing systems are either only designed for single-engine accesses, or impose many restrictions by limiting cross-engine transactions to certain isolation levels and table operations. The result is inadequate cross-engine support in terms of correctness, performance and programmability.