Note that NATS is currently pub/sub, which is a "if a tree falls in the forest" situation. Messages don't go anywhere if nobody is subscribing.

So it's awesome for realtime firehose-type use cases where a websocket client connects, receives messages (every client gets all the messages, although NATS also supports load-balanced fanout) for a while, then eventually disconnects.

NATS is ridiculously fast [1], too.

There's an add-on currently in beta, NATS Streaming [1], which [2] has durability, acking/redelivery and replay, so covers most of what you get from both RabbitMQ and Kafka. It looks very promising.

[1] http://bravenewgeek.com/tag/nats/

[2] https://nats.io/documentation/streaming/nats-streaming-intro...