One of several current trends in distributed database system de- sign is a move away from supporting traditional ACID database transactions. Some systems, such as Amazon’s Dynamo [13],Mon- goDB [24], CouchDB [6], and Cassandra [17] provide no transac- tional support whatsoever. Others provide only limited transaction- ality, such as single-row transactional updates (. Bigtable [11]) or transactions whose accesses are limited to small subsets of a database (. Azure [9], Megastore [7], and the Oracle NoSQL Database [26]). The primary reason that each of these systems does not support fully ACID transactions is to provide linear out- ward scalability. Other systems (. VoltDB [27, 16]) support full ACID, but cease (or.
