1. A method, by one or more computing devices, comprising: receiving, at a computing device, a message including a multimedia file, the message sent by a computing device of a first user; determining a location of the first user; accessing a data store to retrieve a set of social contacts associated with the first user; accessing spatio-temporal information for one or more social contacts identified in the set of social contacts; prior to conducting a face matching procedure based on the multimedia file, ranking the set of social contacts based on spatio-temporal proximity to the location of the first user; and sending identifiers corresponding to the one or more top ranked social contacts in the set of social contacts to the computing device of the first user.