How I cut my AWS bill to $0 by moving my backend to the browser (WebAssembly) (opens in new tab)

A few months ago, I was mapping out the architecture for a heavy file-processing application. The traditional SaaS playbook was obvious: User uploads a heavy file. Store it in an AWS S3 bucket. Spin up an EC2 instance or AWS Lambda function to process it. Send the result back to the client. But when I ran the numbers on processing thousands of 50MB files a day, the AWS bandwidth and compute costs were terrifying. Worse, uploading user files to my servers introduced massive privacy and GDPR li...