Oplog Slave Lag Master Time exceeded threshold #

Meaning #

The replication lag of a secondary is above the alert threshold. This means the secondary couldn’t keep up with the number of writes happening in the cluster.

Impact #

Users may not see recent content, e.g. just created comments seem to appear and disappear between refreshes.

Diagnosis #

This alert is often caused by a high number of writes.

Check Atlas cluster metrics (inspect the replication lag metric for the “secondaries”)

Mitigation #

Identify any unusual processes (e.g. cronjobs, manual processes) and try to pause/stop them.