[wpeterson]

If this system is merely decoding JSON and writing payloads to S3 for asynchronous data processing, why not have your clients write directly to S3?

[blakesmith]

I'm not the author of the article, but if I'd have to guess: Data encapsulation, and interface control. If all your clients are talking directly to S3 instead of your encapsulated service interface, you can't inject any business logic at all and must design around the fact that you don't control the service interface, Amazon does.