1. A method comprising: by a computing device, receiving a content object; by the computing device, determining whether a list configured to store information of a pre-determined number of stored content objects is full, wherein each content object is represented as a vector of elements; by the computing device, identifying a corresponding node of a k-dimensional tree for each of the stored content objects and the received content object based on determining one or more median vectors from the vectors of the content objects, wherein each node of the k-dimensional tree is configured to store the vector of a particular one of the content objects; and by the computing device, moving information corresponding to the vector of one or more of the stored content objects and the received content object from the list to the corresponding node of the k-dimensional tree.