1. A computer implemented method for selecting a set of videos related to a first video, the method comprising: receiving data representative of interactions with videos by a plurality of users; identifying, from the received data for a first video, those interactions that are positive interactions with the first video, the positive interactions indicating user interest in the first video that occurred after playback of the first video began; identifying, from the received data for a plurality of second videos, those interactions that are positive interactions with the plurality of second videos, the positive interactions indicating user interest in the plurality of second videos that occurred after playback of the plurality of second videos began, wherein playback of the plurality of second videos occurred within a locality of time after playback of the first video; generating co-occurring positive interactions for the first video and each of the plurality of second videos based on the identified positive interactions, a co-occurring positive interaction for the first video and a second video indicating interest of a user in both the first video and the second video after playback of the first video and playback of the second video within the locality of time; assigning a weight to each of a plurality of the co-occurring positive interactions for the first video and each of the plurality of second videos, the assigned weight for a co-occurring positive interaction for the first video and each of the plurality of second videos based on a length of time between viewing of the first video and each of the plurality of second videos; storing a count of co-occurring positive interactions for the first video and each of the plurality of second videos based on the weighted co-occurring positive interactions for the first video and each of the plurality of second videos; ranking, by a computer, each of the plurality of second videos using the counts of co-occurring positive interactions; selecting the set of related videos for the first video from the plurality of second videos using the ranked counts of co-occurring positive interactions; ranking, by the computer, the plurality of second videos included in the set of related videos for the first video based at least in part on a total duration of watch time of each of the plurality of second videos by the plurality of users; and storing an indication of the set of related videos.