In our 4th episode, we will discuss on how to build reactive architectures by transitioning from monolithic systems to distributed microservices. It uses a payment processing example to illustrate the shift from synchronous, pull-based interactions to asynchronous, push-based event-driven communication. The benefits of this transition include improved scalability, resilience, and service autonomy. Key concepts discussed are microservices, reactive principles (responsiveness, resilience, elasticity, message-driven), and the advantages of a push model over a pull model.