A team is developing a feature to find the most similar items from a catalog of millions of entries. The entire catalog is converted into a key-value datastore, which is built only once from a fixed, unchanging set of training data. During live operation, the system needs to respond to user queries in milliseconds, but the team finds that searching the datastore for the nearest neighbors for each query is too slow, taking several seconds. Evaluate the team's current implementation strategy. What is the fundamental reason for the poor performance, and what change should they implement to meet the speed requirements, given the nature of their datastore?