NorthScale Membase Server is an elastic key-value database that stores web application data far more efficiently and cost effectively than it can be stored in a relational database. With NorthScale Membase Server, organizations can deploy a highly available, cloud-friendly data layer that expands dynamically as application needs change, delivering performance exceeding that of any other NoSQL solution. API compatible with memcached, the de facto standard web caching software, Membase is easy to use and supported by virtually every programming language and application framework.
Membase gives you an easy way to access and use memcached as a key-value database. Membase is a very powerfull solution if you need a reliable, fast and distribuited cache engine.
The Extension allows you to use Membase as a key/value cache for your Objects (components), Templates, Queries and Resources (such as files etc).
More info can be found in the Railo wiki : http://wiki.getrailo.org/wiki/extensions:membase