[itamarhaber]

Regarding 3 - I don't know if you (or anyone for that matter) are wrong or right about this (or anything), but there are ways to use Redis w/o upgrading to bigger machines. Redis cluster, as mentioned in @bendmorris comment, is one way to go about it.

Alternatively, if you want to continue using Redis - with the current or a slimmer version of the data model - without having to worry about machine upgrades or clusters, then I recommend that you look at http://redislabs.com/redis-cloud (disclaimer - I work at Redis Labs). Our managed service is built using production-proven Redis clusters that allow your database to scale well beyond the limits of any single node, without you having do anything or change a line of code.