Can you explain what you mean? I'm confused about the "might not need the lambda". Thanks!

In my case we allow up to 10mb file upload. For example just testing something right now from my iPhone I selected a 3.7mb image which was uploaded and resized to the "frame" it will go into in the UI and its now 288kb in S3. We have a few "frame" sizes which are consistent throughout our application. Now, my cloudfront is serving 288kb file instead of 3.7mb, which is good for me because I want to avoid the bandwidth costs and users honestly can't tell the difference, and then also we aren't a photo gallery app.

So in my case I need the lambda to resize the image to our "frame" sizes. I wonder if I didn't explain right. I'm ESL so just want to make sure since I'm confused about the your last sentence.