Amazon RDS: plot number of instances in CloudWatch

Question

How do I plot the number of instances in my AWS Aurora RDS cluster over time in CloudWatch?

There doesn't seem to be a metric for that.

Answer 1

Indeed there is no metric for that.

UPDATE: the below trick is not 100% foolproof: when the dashboard range is set to 1d or more, the display period automatically changes to 5 Minutes, which leads to values being off by a factor of 5.

The trick is to pick any RDS aggregated metric (for example CPUUtilization, aggregated per DB role), then select Statistic: Sample Count and Period: 1 Minute.