How to send notification when request comes in?

Hi guys.
I want to implement something like this.

User A can send a job request to User B.
User B get notified for a new request.

I am using Absinthe with phoenix and frontend is react native.
Which technology in elixir or phoenix can I take advantage of?

phoenix channel, phoenix pubsub, absinthe subscription?
Please give me ideas.
Thanks :slight_smile: