The title should have been: AWS Lambda Works as Expected – An Application Architectural Bug [pdf]
If the designer expects a reliable system that guarantees processing of the request after the return of the status, they cannot rely on a server to not crash the moment the response was sent to the wire. Serverless enforces this well, yet people try to force their view of infinitely reliable infrastructure, which is not based in reality.
What does it have to do with S3? Average webpage with JS will weight at about 200kb per initial load, without images. Do the math how many page views and indexing bots will consume before the real user can even find the page.