Asynchronous tasks
A simple event-driven system is one that allows you to execute asynchronous tasks.
The events produced by an event-driven system describe a particular task to execute. Normally, each task will require some time to execute, which makes it impractical to be executed directly as part of the publisher code flow.
The typical example is a web server that needs to respond to the user in a reasonable time. Some HTTP timeouts can produce errors if an HTTP request takes too long, and generally it is not a great experience to respond in more than a second or two.
These operations that take a long time may involve tasks like encoding video into a different resolution, analyzing images with a complex algorithm, sending 1,000 emails to customers, deleting a million registers in bulk, copying data from an external database into a local one, generating reports, or pulling data from multiple sources.
The solution is to send an event to handle this...
