My suspicion is what they're calling "front-end" servers aren't serving static HTTP requests, and their "back-end" servers handle background/offline tasks. And

My suspicion is what they're calling "front-end" servers aren't serving static HTTP requests, and their "back-end" servers handle background/offline tasks. And now that I look again, I realize "they" aren't even connected with TA or Pintrest, just a person who has a somewhat shinier AWS cost calculator.