Abstract. Cloud computing platforms provide scalability and high availability properties for web applications but they sacrifice data consistency at the same time. However, many applications cannot afford any data inconsistency. We present a scalable transaction manager for cloud database services to execute ACID transactions of web applications, even in the presence of server failures. We demonstrate the scalability of our system using a prototype implementation, and show that it scales linearly to at least 40 nodes sustaining a maximum throughput of 7286 transactions per second.