Building an API for performing a complex business action in a composable manner. You may ask why would somebody use it in such a way? The answer is – to build a test framework. It can be tempting to model a business action in form of a builder, but I would like to suggest a new approach.
There is a high need for a concurrent processing and most probably it will become only higher. That is why it is important to know the tools we have at hand, i.e. programming languages and everything around them, which is not limited to merely semantics, syntax, and idioms (though we still should have a solid knowledge of them).