Asynchronous communication leads to looser coupling of the systems. It generally increases the overall responsiveness as well as overhead and enables scenarios where systems are not reliably available all the time. There exist many forms of how to design asynchronous communication, on a conceptual or technical level. Asynchronous communication doesn't imply that there can't be synchronous calls on a technical level. The business process can be built in an asynchronous way that models one or several synchronous invocations that are not performed or handled immediately. For example, an API can offer synchronous methods to create long-running processes that are frequently polled for updates later on.

On a technical level, asynchronous communication is usually designed in a message-oriented way implemented using message queues or the publish-subscribe pattern. Applications only directly communicate with a message queue or a broker, respectively, and messages are not directly passed to a specific receiver.

Let's have a look at the various ways to accomplish asynchronous communication.