An innovative and more secure approach to developing fault-tolerant cloud applications is offered through the groundbreaking cloud-native DBOS operating system. Drawing from three years of collaborative open-source research and development between MIT and Stanford, DBOS transforms the landscape of cloud-native architecture. This cloud-native operating system leverages a relational database to significantly streamline the intricate application stacks commonly found today. DBOS underpins DBOS Cloud, which serves as a transactional serverless platform that ensures fault tolerance, observability, cyber resilience, and straightforward deployment for stateful TypeScript applications. The services of the operating system are built upon a distributed database management system, featuring integrated transactional and fault-tolerant state management that reduces complexity by eliminating the need for containers, cluster management, or workflow orchestration. It offers seamless scalability, outstanding performance, and consistent availability, while metrics, logs, and traces are conveniently stored in SQL-accessible tables. Additionally, the architecture minimizes the cyber attack surface, incorporates self-detection mechanisms for cyber threats, and enhances overall cyber resilience, making it a robust choice for modern cloud applications. Overall, the DBOS operating system represents a significant leap forward in simplifying cloud application development while ensuring high security and reliability.