# AsyncController: Server-side parallelism

> Asynchronous processing of controller actions is very useful on long-running requests, since it avoids thread-blocking while the request is being processed.

Published 2010-12-24 by José M. Pérez · https://jmperezperez.com/blog/asp-net-mvc-async-controller/

I usually face asynchronous WPO from the browser side, for instance making async requests to include Javascript files or AJAX-requesting any other content.

Today I have come across a feature that has been around since ASP.Net MVC 2 and that allows Asynchronous processing of controller actions. It is nicely explained on [Using an Asynchronous Controller in ASP.NET MVC](https://docs.microsoft.com/en-us/previous-versions/aspnet/ee728598(v=vs.100)?redirectedfrom=MSDN) on MSDN website.

It is very useful on long-running requests, since it avoids thread-blocking while the request is being processed. In addition, it exposes AsyncManager, that can be used to increase parallelism in an action by splitting the execution of independent operations.