Thanks for this post! The best way to achieve scalability and high performance is by using distributed .NET caching solution. There are many third party distributed caching solution are available in the market and you yourself has mentioned a few in this post. I also got a chance to use of the caching solution called NCache by Alachisoft. After evaluating this product, my first impression was it is godsend for my app. The thing which I like most about NCache is its wide range of topologies. I recently came to know that they had also released the appliance for Memcached as well. if anybody is interested in it, can also download free version of NCache called as NCache Express.

“Velocity” is a distributed in-memory cache that provides .NET applications with high-speed access, scale, and high availability to application data.

* Caches any serializable CLR object and provides access through simple cache APIs.
* Supports enterprise scale: tens to hundreds of computers.
* Configurable to run as a service accessed over the network or run embedded with the application.
* Supports common cache configurations.
* Supports dynamic scaling by adding new nodes.
* Configurable number of backup copies to provide high availability.
* Automatic load balancing.
* Integration with administration and monitoring tools such as ETW, System Center, etc.
* Provides tight integration with ASP.NET to be able to cache ASP.NET session data in the cache without having to write it to source databases. It can also be used as a cache for application data to be able to cache application data across the entire Web farm.
* Follows the cache-aside architecture (also known as Explicit Caching) for V1. That is, you must decide explicitly which objects to put/remove in your applications and “Velocity” does not synchronize with any source database automatically.
* Support for multiple client languages (for example, PHP, C#, C++, etc.).

For more info visit http://msdn.microsoft.com/hi-in/library/cc645013(en-us).aspx