Distributed Systems Lab
Eleven ideas that only matter once you have more than one machine.
Replication Lag
The gap between 'written' and 'visible'.
The primary has already committed write #40. Drag the lag slider to see what a read from the replica actually returns.
Replication lag400ms
Primary reads
#40
Replica reads
#36
The replica is 4 writesbehind. A user who just wrote and immediately re-read from this replica wouldn't see their own change.