Fly's multi-region capability is BGP Anycast-based, which is vastly superior (and much more complex to deploy, outside of Fly) to DNS-based solutions like GeoDNS.
One example of app-level tooling is the fly-replay header, which permits your app to automatically replay requests in different regions. This works really well alongside the FLY-REGION environment variable that is available to each node. https://fly.io/docs/reference/fly-replay/
Another example of app-level tooling is the availability of NATS Jetstream, a key/value store that is less feature-rich than Redis, but supports multi-region active/active replication. This is a big deal, as Redis doesn't offer it at the free tier, and many others (KeyDB) who advertise it seem to have trouble delivering it when there's more than two regions in play.
One example of app-level tooling is the fly-replay header, which permits your app to automatically replay requests in different regions. This works really well alongside the FLY-REGION environment variable that is available to each node. https://fly.io/docs/reference/fly-replay/
Another example of app-level tooling is the availability of NATS Jetstream, a key/value store that is less feature-rich than Redis, but supports multi-region active/active replication. This is a big deal, as Redis doesn't offer it at the free tier, and many others (KeyDB) who advertise it seem to have trouble delivering it when there's more than two regions in play.