Is it a good practice to use AWS S3 infrequent Access (IA) with cloud front for static website resources?

Question

I am in a position where I have a static site hosted in S3 that I need to front with CloudFront. In other words I have no option but to put CloudFront in front of it. I would like to reduce my S3 costs by changing the objects storage class to S3 Infrequent Access (IA), this will reduce my S3 costs by like 45% which is nice since I have to now spend money on CloudFront. Is this a good practice to do? since the resources will be cached by CloudFront anyways? S3 IA has 99.9% uptime which means it can have as much as 8.75 hours of down time per year with AWS s3 IA.

Answer 1

First, don't worry about the downtime. Unless you are using Reduced Redundancy or One-Zone Storage, all data on S3 has pretty much the same redundancy and therefore very high availability.

S3 Standard-IA is pretty much half-price for storage ($0.0125 per GB) compared to S3 Standard ($0.023 per GB). However, data retrieval costs for Standard-IA is $0.01 per GB. Thus, if the data is retrieved more than once per month, then Standard-IA is more expensive.

While using Amazon CloudFront in front of S3 would reduce data access frequency, it's worth noting that CloudFront caches separately in each region. So, if users in Singapore, Sydney and Tokyo all requested the data, it would be fetched three times from S3. So, data stored as Standard-IA would incur 3 x $0.01 per GB charges, making it much more expensive.

See: Announcing Regional Edge Caches for Amazon CloudFront

Bottom line: If the data is going to be accessed at least once per month, it is cheaper to use Standard Storage instead of Standard-Infrequent Access.