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...