1. A computer-implemented method comprising: as implemented by one or more computing devices configured with specific computer-executable instructions, identifying a set of items associated with an item category from a set of item categories; accessing purchase information for the set of items, wherein the purchase information includes purchase time information identifying when an instance of an item from the set of items was purchased; for individual items in the set of items: identifying users who purchased the item; and creating a computer representation of a unidirectional directed graph of the users who purchased the item based at least in part on the purchase time information, the purchase time information including a relative temporal ordering of one or more item accesses by the users, wherein a first node associated with a first user who purchased the item after a second user is connected with a directed link to a second node associated with the second user, and wherein the directed link points from the first node to the second node thereby configuring the computer representation of the unidirectional directed graph in a reverse temporal order based at least in part on the purchase time information for the item; creating a computer representation of a composite directed graph based on the computer representation of the unidirectional directed graph for individual items in the set of items; performing a graph-based centrality measurement process on the computer representation of the composite directed graph to generate a measure of an extent to which users from a set of users are early adopter users; identifying one or more users as early adopter users based at least in part on the measure of the extent to which users from the set of users are early adopter users, wherein the early adopter users comprise users who purchase items within a threshold release window; determining based at least in part on the composite directed graph that at least a threshold amount of the early adopter users accessed a digital item that is consumed via streaming; and adjusting a number of cache servers configured to cache the digital item based at least in part on the determination that at least the threshold amount of the early adopter users accessed the digital item.