A short article in The Register reported on an Apple meetup talk that discussed how the backend processes that make up the Siri voice query system are run on a cluster of thousands of nodes running Mesos.  This is believed to be one of the largest production deployments of Mesos, which was originally developed at Berkeley in RADLab and AMPLab projects.  The article is at: http://www.theregister.co.uk/2015/04/27/apple_siri_runs_apache_mesos/