1. A computer implemented method for ranking of products, said method comprising: under the control of one or more computer systems configured with executable instructions, training an online ranking function using a boosting algorithm to produce a first ranking score for at least one of a plurality of products to be ranked, the online ranking function having access to one or more online features associated with the products, the online features being stored in an index; training an offline ranking function using the boosting algorithm to produce a second ranking score for the product based at least in part on both (a) offline features and (b) the first ranking score produced by the online ranking function, wherein the offline features are not available in the index; producing, by the offline ranking function, the second ranking score for the product and storing the second ranking score in the index; receiving a search query; obtaining a set of search results to the search query, the set of search results including at least the product; ranking the product in the set of search results based at least in part on both the first ranking score produced in response to the search query and the second ranking score obtained from the index.