1. A computer-implemented method comprising: at a server computer accessible via a data network to a plurality of client computing devices, receiving a digital asset from a client computing device over the data network; generating a feature vector and a unique identifier for the received digital asset; assigning the digital asset to a leaf node of a first search tree data structure maintained at the server computer, the first search tree data structure implemented with a highly scalable graph database and having a root node, one or more internal nodes, and one or more leaf nodes to which digital assets are assigned; and storing the digital asset in association with the unique identifier.