Provisioning serendipitous content recommendations in a targeted content zone

A method comprising:

• generating, by a processing device, a record identifying a set of content items interacted with by a user system, where each content item is associated with one or more topics;
• generating a confidence score associated with each of a set of topics associated with the set of content items, wherein the confidence score represents a quantity of instances a respective topic appears in a collection of content items;
• determining a portion of the set of topics having a confidence score that exceeds a threshold confidence level;
• identifying a candidate serendipitous content item that comprises the portion of the set of topics;
• determining, based on the record, the candidate serendipitous content item has not been interacted with by the user system;
• and
• in response to a request from the user system to access a document of a publisher system, causing a display of the candidate serendipitous content item in a targeted serendipitous content zone of the document.

A non-transitory computer-readable storage medium comprising executable instructions that, if executed by a processing device, cause the processing device to:

• generate a record identifying a set of content items interacted with by a user system, where each content item is associated with one or more topics;
• generate a confidence score associated with each of a set of topics associated with the set of content items, wherein the confidence score represents a quantity of instances a respective topic appears in a collection of content items;
• determine a portion of the set of topics having a confidence score that exceeds a threshold confidence level;
• search the collection of content items for a candidate serendipitous content item that comprises the portion of the set of topics;
• determine, based on the record, the candidate serendipitous content item has not been interacted with by the user system;
• and
• generate at least a portion of a graphical user interface comprising a plurality of content zones having a depth defined based on user engagement measurements, wherein the plurality of content zones comprises a targeted serendipitous content zone comprising the candidate serendipitous content item.