Abstract: Technologies for unseen notification handling are described. Embodiments select an initial set of notifications, provide the selected initial set of notifications to a client device, store seen notifications in a first data store, maintain sent but unseen notifications in a second data store that is an in-memory online data store, retrieve a set of the sent but unseen notifications from the second data store, create a list of unseen notifications by combining the retrieved set of sent but unseen notifications with a set of unsent and unseen notifications, generate a set of relevance scores for the list of unseen notifications, create a new version of the list of unseen notifications based on the new set of relevance scores, and provide the new version of the list of the unseen notifications to the client device.

Abstract: Techniques for broadcasting notifications with low latency are provided. A set of recipients for a notification of a content item is determined. The notification is stored in a second notifications storage that is separate from a first notifications storage. A request for one or more notifications is received over a computer network from a client device that is associated with a particular recipient in the set of recipients. In response to receiving the request, first notification data is retrieved from the first notifications storage, second notification data that includes the notification is retrieved from the second notifications storage. The first notification data is combined with the second notification data to generate combined notification data. The combined notification data is transmitted over the computer network to the client device and is stored in the first notifications storage. The notification may be removed from the first notifications storage.

Abstract: Techniques for broadcasting notifications with low latency are provided. A set of recipients for a notification of a content item is determined. The notification is stored in a second notifications storage that is separate from a first notifications storage. A request for one or more notifications is received over a computer network from a client device that is associated with a particular recipient in the set of recipients. In response to receiving the request, first notification data is retrieved from the first notifications storage, second notification data that includes the notification is retrieved from the second notifications storage. The first notification data is combined with the second notification data to generate combined notification data. The combined notification data is transmitted over the computer network to the client device and is stored in the first notifications storage. The notification may be removed from the first notifications storage.