Event-driven architectures (EDAs) are a software design approach where the flow of the program is determined by events. An event can be any significant change in state, such as a user action, a system update, or a message from another service. This architecture allows different components of a system to communicate asynchronously, improving responsiveness and scalability. In an EDA, components react to events rather than relying on a fixed sequence of operations. This means that when an event occurs, it triggers specific actions in the system, allowing for real-time processing. Common technologies used in EDAs include message queues, event streams, and publish-subscribe systems.