Disclosed are various embodiments for scalable notification deliveries in computing environments. A subscription request is transmitted along with a user identifier, a service identifier, a subscription identifier, and a channel identifier. Notifications are communicated through a notification multiplexing channel between two nodes of a computing environment. The notification multiplexing channel includes notifications multiplexed by subscription identifiers. The notification multiplexing channel corresponds to the channel identifier. A notification corresponding to the subscription identifier is identified and provided to a client computing device associated with the user identifier.