What do UsageQuantity and ResourceRate really represent in Cost Export for Functions?

The UsageQuantity in the Cost Export for Azure Functions represents the amount of the resource consumed during the billing period. For Functions billing lines, this typically refers to the total number of executions or the amount of execution time used, depending on the specific metric being measured.

Regarding your second question, UsageQuantity is not measured in the same units across all tiers of Functions usage (Premium, Consumption, and Flex Consumption). Each tier may have different metrics and units of measurement. For example, in the Consumption plan, it is often measured in GB-seconds, while in other plans, it may vary based on the specific billing model used.

As for the ResourceRate, it can change for the same service due to various factors, including different pricing models, discounts applied, or regional pricing variations. This means that even if the UsageQuantity is the same, the ResourceRate can differ based on these factors, leading to different PreTaxCosts for the same service under different conditions.

In your example, the differences in UsageQuantity and ResourceRate can lead to the same PreTaxCost despite varying UsageQuantities, as the ResourceRate might be adjusted based on the specific conditions of each line item, such as location or pricing agreements.

References:

• Understand cost details fields
• Terms in the Azure usage and charges file for a Microsoft Customer Agreement

Hi @Jamie Wigley,

Thanks for reaching out to Microsoft Q&A.

1. Understanding UsageQuantity:

The UsageQuantity column in the cost export for Azure Functions reflects the amount of execution time your function app has consumed. For Azure Functions, especially in the Consumption plan, this value is typically measured in GB-seconds. This essentially means the total memory (in GB) multiplied by the execution time (in seconds).

2. Measurement Units Across Tiers:

The UsageQuantity should indeed be consistent across the various tiers (Premium, Consumption, and Flex Consumption). Each tier also measures usage in terms of GB-seconds. However, it's important to validate that you’re comparing similar scenarios, because differences in execution time or memory allocation can still lead to different UsageQuantities being reported for similar operations.

3. Understanding ResourceRate Variations:

About the ResourceRate changing for the same service, this can happen due to several reasons:

• Regional Pricing: Different regions might have varying rates due to local pricing policies.
• Different Service Tiers: Even within the same type of service, different performance tiers can affect the ResourceRate.
• Billing Updates: Pricing can change based on updates to Azure's billing structure.

Regarding your observation where UsageQuantities differ but the PreTaxCosts remain the same, this suggests that the rate you're charged might have also varied accordingly, balancing the cost out.

References

• Help me understand my bill and usage
• Estimating consumption-based costs
• On-Demand Function Pricing

Hope it helps!

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