I don't think it would have been enough for this exact situation. The solution you are providing is for cases where x==nil but in their case there was never an x, so you cannot do x==nil checks unless you deliberately set up x.

Not quite. Cloudwatch provides for both behaviors. You can treat periods with no datapoints as “breaching” the threshold criteria. You can also independently alert for “insufficient data” where the source is unavailable, doesnt contain enough data to evaluate, etc.

In the past I did both. Always emit a 0 datapoint every period + treat missing datapoints as breaching to discover if an application wasnt consistently emitting metrics. In addition a lower severity Insufficient Data alert was used to discover/validate when a meteic stream literally didnt exist (normally through misconfiguration of metric & alarm dimensions).

Docs: https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitori...

Yep, and Grafana allows alerting on No Data states.