It feels like the diamond in the story is the insertion of randomness in the backoff/retry. Networking protocols have an awkward habit of not doing this and acc

It feels like the diamond in the story is the insertion of randomness in the backoff/retry. Networking protocols have an awkward habit of not doing this and accidentally inducing thundering herds of retries. In the till situation, classic expo backoff would have been catastrophic: since all tills at Xmas are about equally busy, they'll all backoff and retry in the same way. So the randomness essentially simulates different levels of till busyness.