Caching web page images when origin is set to alb for Cloudfront

Yes, it is possible to cache images with CloudFront when using an Application Load Balancer (ALB) as the origin. However, you'll need to make some additional configurations to ensure proper caching.

By default, CloudFront may not cache your images due to the origin's cache control headers or CloudFront's default cache behavior. To enable caching for your images when using an ALB as the origin, consider the following steps:

1. Configure Cache Control Headers: Ensure your web server (behind the ALB) is sending appropriate Cache-Control headers for the images. These headers instruct CloudFront on how long to cache the content.

2. Use Managed Cache Policies: CloudFront offers managed cache policies that can help with caching. For your use case, you might want to use the "UseOriginCacheControlHeaders" policy. This policy instructs CloudFront to respect the Cache-Control headers sent by your origin (web server).

3. Custom Cache Policy: If the managed policies don't meet your needs, you can create a custom cache policy. This allows you to specify which headers, cookies, or query strings should be included in the cache key.

4. Origin Shield: Consider enabling CloudFront Origin Shield. This adds an additional caching layer that can improve your cache hit ratio and reduce the load on your origin.

5. Minimum TTL: In your cache behavior settings, ensure the Minimum TTL is set to a value greater than 0 if you want to force some level of caching.

6. Object Caching: In the CloudFront distribution settings, make sure you've selected "Use Origin Cache Headers" for the Object Caching setting.

Remember, the effectiveness of caching also depends on the nature of your images. If they are frequently changing or personalized, you may need to adjust your caching strategy accordingly.

By implementing these configurations, you should be able to successfully cache your images in CloudFront, even when using an ALB as the origin.

Sources
Amazon CloudFront announces managed cache policies for web applications - AWS
Using Amazon CloudFront Origin Shield - Amazon CloudFront
Caching and availability - Amazon CloudFront