A centralized document system identifies content items for presentation to a user based initially on a cold-start algorithm and subsequently based on machine-learned models. The system detects a first access by the user. The system generates a user attribute vector for the user and a content vector for each content item. The system selects a first content item based on the initial cold-start algorithm and modifies a user interface to include the first content item. The system identifies an interaction with the first content item by the user. The system detects a second access by the user. The system selects a machine-learned model based on a set of interactions by the user with displayed content items. The system applies the selected machine-learned model to the set of interactions and the user attribute vector to identify a second content item and modifies the user interface to include the second content item.