Replication may occur as often as every minute, but you could still lose files or changes within that time span that were never copied to the target.
I think Veeam limits to every 15 minutes?
I don't know as we don't use Veeam replication. I know other solutions can go as often as every minute. But that is outside of this scope.
Some every 30 seconds.
DRBD does it in milliseconds, as fast as the platform can do it.