In an event-driven architecture, organizations can automate their serverless applications by making them responsive to certain input events, allowing for asynchronous handling of incoming events and effective decoupling of application components. This is achieved using AWS Lambda functions, which listen for incoming events and process them in the application code. The key AWS services used in this setup include Amazon EventBridge as an event bus service, Amazon DynamoDB as a NoSQL database service, and AWS Lambda itself as a serverless, event-driven compute service. By creating an event-driven microservice that stores information about incoming online orders, organizations can save costs by charging resources based on usage and focus more on designing and building applications. The setup involves creating an IAM role for the Lambda function, setting up a DynamoDB table, and configuring an EventBridge rule to trigger the Lambda function with incoming events from Microservice X. Testing the event-driven setup involves sending a test event through the EventBridge console and verifying that it invokes the Lambda function correctly, which then stores the information in the DynamoDB table. This is a prime example of an event-driven architecture that works in real-time to process incoming event streams.