Simple definition
Active Directory replication latency is the delay before a directory change reaches another domain controller.
Purpose and use
AD replication latency measures the delay for a change to reach other replicas that should receive it.
How does it work?
It depends on notifications, schedules, topology paths, load and communication availability, particularly between sites.
Example and verification
For a change visible on only one controller, compare state and metadata across relevant replicas and inspect recent exchanges.
Points to watch
Successful authentication on one controller does not prove that all others already share its state. Prolonged delay can create risks beyond a display discrepancy.
In short
Measure an identified change and partition using consistent timing and comparison scope.