A method is provided for retrieving information from massive databases (i.e., databases with millions of documents) in real time, that allows users to control the trade-off between accuracy in retrieved results and response times. The method may be applied to databases with contents, i.e., documents which have been modeled with a clearly defined metric that enables computation of distances between any two documents, so that pairs of documents which are "closer" with respect to the metric are more similar than pairs of documents which are "further apart". Our method can be applied to similarity ranking and/or can be combined together with other methods to increase the scalability of information retrieval, detection, ranking, and tracking.