Strange spike in CloudFront cost

Question

First off, I am a complete newbie with AWS. We set up an account to use S3/CloudFront as our Content Delivery Network for streaming video clips on our website. So far our monthly costs have been extremely reasonable - until our Dec bill where we saw a spike in cost, related to CloudFront costs specifically. Looking at the Cost Explorer, the spike seems specific to a short time period between Dec. 22-31, and as of Jan 1 the spike is gone (see screenshot). Any thoughts on how to understand what caused that spike in usage/cost, other modules/areas to drill down for detail?

CloudFront cost spike

![CloudFront cost spike](/media/postImages/original/IMvr9qjLCUTz6hJWa2qdoOyQ)

Answer

In addition to what @Didier_Durand mentioned around CloudFront logs, you can also get some clues from Cost Explorer. If you filter to only show the Service CloudFront and Group By Usage Type, you should see what constituted the CloudFront charges.

Give this happened at the end of the month and then disappeared, I suspect that your [CloudFront free tier ](https://aws.amazon.com/free/?all-free-tier.sort-by=item.additionalFields.SortRank&all-free-tier.sort-order=asc&awsf.Free%20Tier%20Types=*all&awsf.Free%20Tier%20Categories=*all&all-free-tier.q=cloudfront&all-free-tier.q_operator=AND) was exhausted.

There is an [article tracking free tier usage.](https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/tracking-free-tier-usage.html) You may want to enable an alert to tell you about free tier usage being exhausted.

Answer

Hi,

To start understanding such traffic splikes, you need to analyze the CloudFront standard logs and dive deeper from there: https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/AccessLogs.html#access-logs-analyzing

This blog post details how to do it with CloudWatch: https://aws.amazon.com/blogs/mt/sending-cloudfront-standard-logs-to-cloudwatch-logs-for-analysis/

Best,

Didier

Strange spike in CloudFront cost

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