Unexplained Increase of 2519.03% in API Gateway Costs - DataTransfer-Out-Bytes

Question

Dear AWS Support Team,

I have been using my AWS account for the past 3–4 years without any significant changes to our usage or user base. However, over the past month, we've observed a substantial and unexpected increase in our API Gateway costs, specifically related to DataTransfer-Out-Bytes.

Historically, our data transfer usage was approximately 70.703 GB (costing USD 6.36). However, last month it surged to 1,850.812 GB (costing USD 166.57), representing an increase of over 2519.03%. This change is baffling as there have been no increases in traffic, number of users, or any alterations in our API usage patterns that would justify this spike.

We kindly request your assistance in investigating this issue, as the increased costs are disproportionate and seem to indicate a potential anomaly or misconfiguration.

Please let us know if you require any additional details or logs to assist in your investigation.

Thank you for your attention to this matter.

re:Post Agent · Answer

I understand your concern about the unexpected increase in API Gateway costs, particularly related to DataTransfer-Out-Bytes. This significant jump from 70.703 GB to 1,850.812 GB without any apparent changes in your usage patterns or user base is indeed unusual and warrants investigation.

To address this issue, I recommend the following steps:

1. Use AWS Cost Explorer to analyze your API Gateway usage in detail. Filter your view to focus on DataTransfer-Out-Bytes for API Gateway. This will help you visualize the trend and pinpoint when the spike occurred.

2. Group the data by resource in Cost Explorer. This will allow you to identify if the increased usage is associated with a specific API or stage within your API Gateway setup.

3. Check your API Gateway logs and metrics in Amazon CloudWatch. Look for any unusual patterns in the number of requests, response sizes, or specific endpoints that might be generating more traffic than expected.

4. Review your API Gateway configuration for any recent changes that might have affected data transfer. This could include modifications to integration responses, enabling CORS, or changes in how your API handles large payloads.

5. Investigate if there have been any changes in how your backend services respond to API requests. Sometimes, backend changes can result in larger response sizes without obvious changes to the API itself.

6. Use AWS Cost Anomaly Detection to set up alerts for future unexpected cost increases. This service can help you identify and respond to unusual spending patterns more quickly.

7. Consider implementing AWS Budgets to set cost thresholds and receive notifications when your spending approaches or exceeds these limits.

If after these investigations you're still unable to identify the cause of the increase, it would be advisable to open a support ticket with AWS for a more in-depth analysis. They may be able to provide additional insights or identify any potential issues with the service itself.

Remember, it's crucial to regularly review and analyze your AWS costs to catch and address such anomalies quickly. Implementing proper cost management practices can help prevent unexpected expenses and ensure optimal use of AWS resources.  
**Sources**  
[Extended history and more granular data available within AWS Cost Explorer | AWS Cloud Financial Management](https://aws.amazon.com/blogs/aws-cloud-financial-management/extended-history-and-more-granular-data-available-within-aws-cost-explorer/)  
[COST05-BP06 Perform cost analysis for different usage over time - AWS Well-Architected Framework (2023-04-10)](https://docs.aws.amazon.com/wellarchitected/2023-04-10/framework/cost_select_service_analyze_over_time.html)

Unexplained Increase of 2519.03% in API Gateway Costs - DataTransfer-Out-Bytes

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