CloudWatch Metric Math: Creating 24-Hour Rolling Sum for SES Daily Quota Monitoring

Question

I'm trying to create a CloudWatch alarm that monitors Amazon SES daily sending quota usage with a true 24-hour rolling window (similar to how AWS calculates SES quotas). The goal is to alert when usage reaches 80% of the daily quota.

The standard approach using Period: 86400 and EvaluationPeriods: 1 creates a fixed 24-hour window aligned to calendar boundaries, not a continuously rolling 24-hour window that updates every hour.

Question:
Is there a way to use CloudWatch Metric Math to create a true 24-hour rolling sum?

Example Use Case:
- SES Send metric: 100 emails at hour 1, 200 at hour 2, etc.
- At hour 25: Rolling sum should be hours 2-25 total, dropping hour 1
- Alarm triggers when rolling sum exceeds 80% of daily quota

Does CloudWatch Metric Math have any functions or combinations that can achieve this rolling window behavior natively, or is a custom Lambda-based solution the only viable approach?

Ava Thompson · Accepted Answer

Unfortunately, CloudWatch Metric Math can’t create a true rolling 24-hour window on its own. The 24-hour period you set in CloudWatch is fixed to the calendar day — it doesn’t slide forward hour by hour like AWS SES does for quota tracking.

Here’s what you can do instead:

Use a Lambda function:

Set up a Lambda (via EventBridge) to run every hour.

Have it pull the last 24 hours of SES “Send” metrics using the GetMetricData() API.

Calculate the total sends from the past 24 hours and push that number to a custom CloudWatch metric.

Create an alarm based on that custom metric to trigger when it hits 80% of your quota.

Or use the SES API directly:

The GetSendStatistics API gives data that already matches SES’s rolling 24-hour window.

You can use that for alerts or dashboards instead of trying to simulate it in CloudWatch.

re:Post Agent · Answer

Yes, you can create a true 24-hour rolling sum for SES quota monitoring using CloudWatch Metric Math.

Amazon SES sending quotas are calculated on a rolling 24-hour period, where AWS determines the number of emails you've sent in the previous 24 hours each time you try to send an email. To mirror this behavior in CloudWatch, you can use metric math expressions.

Here's how to approach this:

1. Use a 1-hour period for your base SES sending metric (this gives you hourly data points)
2. Create a metric math expression that sums the last 24 data points
3. Set up your alarm on this expression

The key is to use a metric math expression that performs a rolling sum over the last 24 hours. When CloudWatch evaluates alarms, it aggregates periods into single data points, which allows you to create this rolling window effect.

For your alarm configuration:
- Set the Period to 1 hour (3600 seconds)
- Use a metric math expression that sums the last 24 data points
- Set the alarm threshold to 80% of your daily quota
- Configure appropriate evaluation periods (e.g., 1 out of 1)

This approach will give you a continuously updating view of your SES usage over the past 24 hours, similar to how AWS calculates the quota internally. The alarm will trigger when your rolling 24-hour usage exceeds 80% of your daily quota, giving you time to take action before hitting your limit.

You can create this alarm directly through the Service Quotas console, which provides a simplified interface for setting up CloudWatch alarms on service quotas, including SES sending quotas.  
**Sources**  
[Managing your Amazon SES sending quotas - Amazon Simple Email Service](https://docs.aws.amazon.com/ses/latest/DeveloperGuide/manage-sending-quotas.html)  
[Create a CloudWatch alarm based on a metric math expression - Amazon CloudWatch](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/Create-alarm-on-metric-math-expression.html)  
[Service Quotas and Amazon CloudWatch alarms - Service Quotas](https://docs.aws.amazon.com/servicequotas/latest/userguide/configure-cloudwatch.html)  
[Custom metrics and extended metrics that you can send to CloudWatch - Amazon CloudWatch](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch-RUM-custom-and-extended-metrics.html)

Jsc · Answer

Hi,

I am very puzzled by the question and answers given here, as CloudWatch does create a sliding window by default.
CloudWatch behaviour is exactly the opposite of what you describe: using Period 86400 and EvaluationPeriods 1 creates a continuously rolling 24-hour window where the window slides every minute!
If you experience something different, did you check that the metric is indeed refreshed? Otherwise, you might need to please share more details about your use case, as CloudWatch does evaluate sliding window.

CloudWatch Metric Math: Creating 24-Hour Rolling Sum for SES Daily Quota Monitoring

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