Proto.Cluster.PubSub is already available for Proto.Actor C#, but is still in experimental stage.
This feature allows developers to publish messages to topics, and then have those messages delegated to subscribing actors.
Those subscribers can be both standard actors with a PID, or cluster actors with a ClusterIdentity
Subscriptions are durable and will be kept between restarts, where the persistence is handled by injectable dependencies. e.g. a Redis
As of now, PubSub is fully Acked, meaning that when a publisher receives an ack, you are guaranteed that the message reached all subscribers. At-Least-Once delivery. which can be used together with out deduplication middleware to guarantee exactly-once-(successful*) delivery.