Abstract: A system is provided for retargeting advertisements and is based on a database storing user behavior data related to information for a plurality of consumers. An index-lookup processes the user behavior data and translates the user behavior data into a plurality of indices. A data loading module processes the plurality of indices and generates a multi-indexed user behavior cube. An online query module receives a request for an advertisement and processes the request to determine one or more related user attributes and retrieves user behavior data from the multi-indexed user behavior cube using the related user attributes. An ad recommendation module receives the set of user behaviors and generates a list of recommended advertisements using the set of user behaviors data and an advertiser retargeting criterion.