Seems to me like there are still plenty of relationships in a chat app. Postgres can be used like a NoSQL database via JSONB too if you want. I think the truth

Seems to me like there are still plenty of relationships in a chat app. Postgres can be used like a NoSQL database via JSONB too if you want. I think the truth is that you should use the simplest, most effective tech possible until you are absolutely certain you need something more niche.