This is awesome.
One genuine question from someone with no context into their product: does Fly lock me in by barring access to WAL replication? This is something Heroku does that is extremely annoying as you'll grow and grow with them and one day you realize migrating the data will be a massive hassle.
We do not! You have full administrative access to your postgres. You can create offsite replicas, or even fork the Postgres app we use and deploy over your Fly.io installed postgres: https://github.com/fly-apps/postgres-ha
RDS preventing external streaming replicas is the most annoying thing ever.