I have an Application Load Balancer whose data transfer cost I want to monitor.

In Cost Explorer, I can filter on usage type "DataTransfer-Out-Bytes", and see how many GB of data it is sending, and how much that costs. I'd like to see that same number in CloudWatch metrics, but I can't find any corresponding metric. The Per-AppELB "ProcessedBytes" metric sounded promising, but that number is slightly more than half the number I see in Cost Explorer. (My best guess is that TLS handshake overhead isn't included.)

Is there any metric or combination of metrics that matches what I end up getting billed for?

  • When inspecting the ProcessedBytes metric in CloudWatch, which statistic are you using? The default statistic is Average, while for this metric, you want the Sum statistic.
    – markusk
    Jul 30 '19 at 0:28

If your main objective is to monitor costs, and it's not crucial that CloudWatch is involved, you could create an AWS Budget with a suitable budget filter. Budgets provide dashboards and notifications for actual and forecasted spend.

  • Thanks, I didn't know about that! It seems like budgets have the same drawbacks as Cost Explorer: data is delayed, and presented in daily granularity. As CloudWatch can display ProcessedBytes with minute granularity, I was hoping that it could display the number I'm actually billed on in the same way.
    – legoscia
    Aug 8 '19 at 11:16

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