Hello,
I have a pretty high traffic Heroku app and I’d like the ability to slowly shift traffic over to fly. Is there any guidance for safe ways to do this? I’d like to avoid a big bang cut-over
If you’re using Heroku Postgres, you should be able to deploy Fly and connect to Postgres directly. That said, you might see a bit of latency. So it’s worth testing from the closest region, which would be iad. From there, users have reported 1-2ms latency.
The harder part would be balancing traffic somehow. Depending on your DNS provider, you might be able to do this via DNS by adding two IP addresses to your domain. In a standard DNS setup, this would send approximately half your traffic to Fly. Services like AWS Route53 offer weighted DNS for more fine-grained control.
What I’d recommend is to deploy on Fly using Heroku Postgres, then run some load tests against your highest traffic endpoints. If you’re satisfied with the results, you could then look into a service that helps you slowly route traffic over like Route53.
Finally, migrating a database over is a whole different story, which we can discuss as needed 
Thanks a lot Joshua. I just wanted to see if there was some tooling available via fly that made this easier. I had been looking into Cloudflare, but thanks for the R53 pointer 