CloudBees is the only cloud company focused on servicing the complete develop-to-deploy lifecycle of Java web applications in the cloud – where customers do not have to worry about servers, virtual machines or IT staff. The CloudBees platform today includes DEV@cloud, a service that lets developers take their build and test environments to the cloud, and RUN@cloud, which lets teams seamlessly deploy these applications to production on the cloud.
Just a quick update: sticky sessions (also known as session affinity) are now available for apps on CloudBees. This means that the CloudBees load balancing can "stick" users to backends if that is what your application (or your preferred framework) requires.
You can read more about how to turn sticky sessions on here - there isn't much to it - turn it on, or not!
It is worth remembering that along with load balancing, there are goodies like auto-scale, app clustering (and session store), and zero downtime deployments to read about and enjoy (don't worry, you don't have to do much). Databases are always master/slave pairs, backed up for you - all of this helps a little bit for HA and scalability, when you need it.
Note also there is this handy excuse generator (not affiliated with CloudBees), should you need it.