what happen when your cash fails what happen when you your cash goes down all of the sudden the Thousand the 10,000 QPS are going to go to your backend system and you can enter this mode where you have a cascading failure where your backend system Falls over and the solution to to recover is to use your cash but you can't put the data back to the cash because you can't read your back end so whenever you start introducing caching to to your application you really need to think through those problem and there is scenario where using a cache is probably not necessary