Core nats is ephemeral. Jetstream is meant to be persisted, and presented as a replacement for kafka

> NATS data is ephemeral in many cases anyhow, so it makes a bit more sense here

Dude ... the guy was testing JetStream.

Which, I quote from the first phrase from the first paragraph on the NATS website:

    NATS has a built-in persistence engine called JetStream which enables messages to be stored and replayed at a later time.

So is MQTT, why bother with NATS then?

MQTT doesn't have the same semantics. https://docs.nats.io/nats-concepts/core-nats/reqreply request reply is really useful if you need low latency, but reasonably efficient queuing. (making sure to mark your workers as busy when processing otherwise you get latency spikes. )

You can do request/reply with MQTT too, you just have to implement more bits yourself, whilst NATS has a nice API that abstracts that away for you.

oh indeed, and clusters nicely.