Building an activity and notification stream for a social network application

As the title suggests, currently my social network backend is in NodeJs with MongoDB and I am looking to add celery + RabbitMQ with Postgres/Cassandra for the activity feed/notification as message queue on fanout based. Do I am approaching my problem in correct way or do I have to look for something like Kafka or else? I am also in mixed of doubts where does my broker should be like my backend serves REST API for different clients. Do clients directly updates data by producing and consuming simultaneously or just consume data while using REST for adding "post/comments"

Need some insight on the way to approach realtime feed problem like the way of Facebook, Instagram or Reddit, etc