Introduction

An event is an action that causes a change of state. This state change can be simple or complex, but when a state changes, this is considered an event. In the event-driven architecture approach, consumers subscribe to events and can receive notifications when they occur. This contrasts with the traditional server-client model, in which a client actively requests updates on a set of information. This model solves a simple problem – how can we notify consumers of status changes? The message-based approach solves this same problem but in a different way than the traditional server-client model. The simple idea behind the message-based approach is that instead of consumers subscribing to event updates, individual elements or services can have message queues with many calls. These calls are ordered and sent to all parties.

To summarize, instead of having an event creating a service through a notification, a message queue takes an event or output that requires additional...