DBOS Transact is an open-source library designed for Python and TypeScript that facilitates durable execution with its built-in once-and-only-once code execution feature, making it ideal for applications like payment processing and data management. By handling retries and recovery procedures automatically, it allows developers to focus on writing business logic without the need for complex error-handling code. The library guarantees that programs will run to completion and each operation will execute precisely once, offering complete auditability. DBOS Transact achieves this by recording key application steps in a database, enabling interrupted applications to resume seamlessly. Developers can use decorators to gain features like durable workflow execution and automatic observability, and applications built with DBOS Transact can run on any platform with a PostgreSQL-compatible DBMS. DBOS Cloud is recommended for production deployment, providing benefits such as serverless deployment, automatic scaling, and advanced debugging capabilities.