Just a quick update: sticky sessions (also known as session affinity) are now available for apps on CloudBees. This means that the CloudBeesload balancing can "stick" users to backendsif that is what your application (or your preferred framework) requires.
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 controller/agent 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.
Michael Neale, Elite Developer