Developed a subscription-based messaging system for the atlanhq/application-sdk repository, focusing on event-driven processing using Dapr PubSub and FastAPI. The solution enabled both synchronous and asynchronous message handlers, supporting bulk message processing to enhance throughput. By integrating dead-letter topics, the system improved fault tolerance and ensured reliable message delivery, even in failure scenarios. The implementation leveraged Python for backend development and emphasized robust failure handling through dead-letter routing, preventing message loss. This work strengthened the scalability and reliability of message-driven workflows, providing a foundation for more resilient event-driven architectures within the application SDK during the development period.