replication solutions wont work because developers will be making changes to the dev environment, so once they change something then the databases are no longer in sync. Nightly backup and restore are the only ways to ensure the data is the same between Dev, Stag, and Prod.

The only other option may be data compare by red-gate, but that would likely be a slow option. May be worth testing with a free trial.

I would recommend trying to speed up the backup & restore process:

- Backup to solid state drives / faster disks.

- increase bandwidth between servers. 10GB cross connect

- compare red-gate compression to SQL Server compression. Compare compression ratio and speed.