Event streaming systems like Apache Kafka often require exactly-once semantics to ensure data integrity by processing events precisely once without duplicates or omissions. Achieving this in distributed systems is challenging and typically defaults to weaker guarantees, as Kafka natively supports exactly-once semantics only for stream processing. Developers often have to create complex architectures to achieve this, but the open-source TypeScript framework DBOS Transact simplifies the process by facilitating idempotency. DBOS Transact allows for exactly-once event processing through transactions and workflows by using an idempotency key constructed from a message's topic, partition, and offset, ensuring reliable message processing even in cases of interruptions, crashes, or failures. The framework provides synchronous and asynchronous processing options, ensuring that duplicate messages do not result in repeated processing. Developers can implement this functionality using TypeScript by writing event processing code with DBOS Transact's straightforward setup, which involves annotating methods and classes to specify Kafka topics and brokers for message consumption.