Creating an event-driven architecture

Event-driven architecture helps you to chain a series of events together to complete a functional flow. For example, when you are making a payment to buy something on a website, you are expecting to get your order invoice generated and to get an email as soon as the payment is complete. Event-driven architecture helps to rope in all of these events so that making a payment can trigger another task to complete the order flow. Often, you will see message queues, which you learned about in the previous section, as the central point while talking about event-driven architecture. Event-driven architecture can also be based on the publisher/subscriber model or the event stream model.

Publisher/subscriber model

In the publisher/subscriber (pub/sub) model, when an event is published, a notification is sent to all subscribers, and each subscriber can take the necessary action as per their requirements of data processing. Let's take an example...