Review evidence is very sparse, but the available founder feedback is positive and practical. The clearest comment comes from the makers of Seagull, who say Fly.io made it trivial to launch their Golang API. Beyond that, other founder entries include ratings without written detail, and there are no user reviews here to confirm or challenge that view. So the narrow takeaway is that founders who mentioned Fly.io see it as straightforward for deployment, especially for a backend API use case.