Asynchronous is a programming pattern which provides the feature of non-blocking code i.e do not stop or do not depend on another function / process to execute a particular line of code.

Asynchronous is great in terms of performance, resource utilization and system throughput. But there are some drawbacks:

• Very difficult for a legacy programmer to proceed with Async.
• Handling control flow is really painful.
• Callbacks are dirty.

If you are a function-oriented programmer, then it would be little difficult for you to grasp asynchronous programming. However, if you are familiar with multithreading in Java, then this is similar to that.