The RR data center and the RR back end communicate on a regular basis, bringing logs of user activity to the back end and updates to the runtime to the data centers. Each data center has an exact copy of the current runtime, so it doesn’t matter which data center is called from the browser.
More data comes to the RR back end from feeds (catalog updates, offline purchase data, etc.). The Relevance Cloud dashboard also configures the back end. Changes from these sources propagate to the data centers through regular updates. (For example, a catalog update that came in through the feed will affect the recommendations in the runtime.)