Abstract: A method and system fulfills ad requests for delivery of ads to mobile clients in a mobile network. Ad data silos for ad requesters are maintained. The ad data silos are organized according to selected characteristics of the mobile clients of the ad requesters. In response to an incoming request for delivery of an ad, an attempt to fill the incoming request includes at least one of (1) retrieving an ad from a corresponding ad data silo to fulfill the incoming request, and (2) retrieving an ad according to a first priority policy from ad source among the plurality of ad sources to fulfill the incoming request. Also, in response to the incoming request, or other signals that may indicate current activity by the ad requester, an ad is retrieved according to a second priority policy for filling the corresponding ad data silo.