This (or equivalent) will happen. You can either design your software to handle it correctly, or you can have buggy software. Clock sync doesn't really help, e

This (or equivalent) will happen. You can either design your software to handle it correctly, or you can have buggy software. Clock sync doesn't really help, especially if a request can trigger multiple independent action that can individually succeed or fail. The simplest example where this goes wrong is posting a post on Reddit. You write your text into a text box and submit. You get an Error 500. You cannot know if your post went through (even if you go check whether your post is visible, sometimes the replica that you got your response from hasn't gotten your post yet). And they don't do any deduping, so if you just retry, you may end up with multiple copies of your reply.