Why do I receive notifications from alert subscriptions even when it’s below the threshold in AWS anomaly detection?

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The issue

In AWS cost anomaly detection, I set up an alert subscription to receive notifications when the threshold is exceeded.
However, I continue to receive notifications even though the cost has fallen below the threshold.
Why do I receive notifications from alert subscriptions even when it's below the threshold in AWS anomaly detection?

The solution

Possible causes for receiving notifications even when below the threshold include the impact of machine learning for cost anomaly detection and the impact of the billing application in Cost Explorer.
Please monitor the situation for a few days after falling below the threshold and confirm that the notifications stop.

Even if an anomaly is below the alert threshold, the machine learning model continues to detect spend anomalies on your account.

AWS official documentation.

In the current billing period, the data depends on your upstream data from your billing applications, and some data might be updated later than 24 hours.

AWS official documentation.

References

• Getting started with AWS Cost Anomaly Detection - AWS Cost Management
• Exploring your data using Cost Explorer - AWS Cost Management