It's strange to me that they still haven't offered a managed Postgres product. Other providers like Render or even Heroku seem to have realized that this is a core part of PaaS that customers want. Instead they focused on GPUs and LiteStream. When I evaluated different PaaS for the startup I work at, I had to go with Render. I couldn't even give Fly.io a try since I knew we needed Postgres.
It think they are in beta. I wished they had a managed Redis though
For Postgres I ended up going with Neon (neon.tech), very happy with them so far. Super easy to setup and get up and running, also love being able to just easily see the data from their web interface