fly.io is a platform that allows you to quickly deploy application code into the cloud. To deploy you need a free fly.io account and the
flyctl command line tool.
There used to be similar a free hosting service called Heroku, that got bought by Salesforce.
The free resources include 3x 1 small CPU, which can be used for a code deployment or a Postgres database.
The documentation include working examples for most programming languages. I was able to get a Go app running and Postgres very quickly. Postgres used a recent version.
Fly apps are connected by a mesh of Wireguard tunnels using IPV6.
The fly.io applications are all connected into a private network with Wireguard. This approach allows to connect multiple services/vms/databases without having to know about the underlying infrastructure. And you can connect to this Wireguard network.
Verdict: is it production ready?
Yes, I think it is a good match for small applications that do not have too many requirements. The platform also can do Postgres snapshots for backup and Wireguard for VPN, which reduces your time for maintenance.
I recommend to develop und run all applications as a container (Dockerfile). This allows to be independent of the platform and migrate away once it outgrows the offerings of fly.io.