Feedback based controller for varying content item density

A method performed by a content delivery system, the method comprising:

• storing a first minimum gap value that indicates a minimum number of slots, in a scrollable content item feed, between two content items that are of a first type and that are from different content providers that are separate from the content delivery system, wherein the scrollable content item feed is presented on a screen of a computing device of a user and contains content items of a plurality of types that includes the first type and a second type that is different than the first type, wherein multiple content items in the scrollable content item feed are presented concurrently on the screen of the computing device;
• using the first minimum gap value to place, in real-time, content items in a first plurality of scrollable content item feeds;
• for each scrollable content item feed of the first plurality of scrollable content item feeds, generating performance data that includes one or more measures of performance of content items of the first type in said each scrollable content item feed;
• based on the performance data and the first minimum gap value, generating a second minimum gap value that is different than the first minimum gap value;
• using the second minimum gap value to place, in real-time, content items in a second plurality of scrollable content item feeds;
• wherein the method is performed by one or more computing devices.