Biasing selection of advertising based on real-time user interactions in a social networking system

A method comprising:

• receiving advertising data describing a plurality of advertisements;
• determining one or more ad topics associated with each of the plurality of advertisements;
• generating a topic index that associates the plurality of advertisements with one or more ad topics associated with each advertisement;
• receiving data describing one or more actions performed by a user of a social networking system;
• determining one or more user topics based at least in part on the one or more actions;
• selecting one or more candidate advertisements based on the one or more user topics and one or more ad topics associated with each of the one or more candidate advertisements according to the topic index;
• generating an expected value for each of the one or more candidate advertisements;
• selecting an advertisement from the one or more candidate advertisements based at least in part on the expected values;
• and
• sending the targeted advertisement to a client device associated with the user for presentation to the user.