Use the Replication Lag alert in Mini DBA to monitor PostgreSQL instances and make this condition visible before it becomes a wider database incident.
Mini DBA describes this alert as: Lag In Seconds Seconds it takes to replicate from this instance to a secondary and be notified secondary has applied transaction. This may indicate periods of very high activity on secondary or bad network conditions. The default evaluation frequency is Minute, so the alert is intended to be close enough to operational reality for live triage.
This alert protects high availability and disaster recovery by warning when replicas, replication slots, or apply processes fall behind. Lag can turn a planned failover into data loss risk or leave reporting users looking at stale data.
Enable it where replication, read replicas, failover, or reporting copies are part of the service design. Disable it on standalone systems that do not use replication so the alert list stays focused.
Threshold meaning: Seconds. Major threshold: 60 seconds. Minor threshold: 30 seconds. Comparison direction: "over". Use higher thresholds on batch-heavy, development, or intentionally bursty systems where brief pressure is expected. Use lower thresholds on latency-sensitive production systems, small instances with little headroom, and services with strict recovery or availability commitments.
Check the sender, receiver, apply process, network path, and oldest retained log position. Restart failed replication workers only after capturing the error, then address the root cause such as disk pressure, long transactions, schema drift, network latency, or insufficient replica capacity.
If this alert is noisy, check whether the workload naturally has short bursts. Raise the duration or threshold for expected batch windows, but keep a lower route for production systems where user-facing latency matters. Avoid simply disabling the alert until you know whether the noise is caused by threshold choice or by a real capacity trend.