SimpleX is based around queues. Instead of pushing everything to a relay and have it stay there forever, you push messages into a queue that eventually gets consumed by the person you’re sending the messages to. They exist on the relay temporarily and they are encrypted. Cool part is that there are no long-term “addresses” or “pubkeys” to send the message to, so spam is much harder.

I think nostr could learn a lot from this protocol, I believe we can use something like this to strengthen use cases on the nostr side. I am building a SimpleX rust library to learn the protocol further, and will be looking into how we can leverage it in our apps.