Live Migrate allows for migrations from non-Atlas clusters into Atlas by syncing data from the source to the Atlas destination, and then cutting over the application to direct workload to the destination.

It's possible to test the application on the destination before cutover, but after cutover, there's no way to sync data in reverse in case unforeseen issues arise and it's necessary to fall back to the source (or another) cluster again.

Having a "fallback sync" option could help with this.