No different from "the team that built that is all gone, they left no doco, we assumed X, added the feature you wanted, but Y happened under load" , which happe

No different from "the team that built that is all gone, they left no doco, we assumed X, added the feature you wanted, but Y happened under load" , which happens a lot in companies pushing to market older than a minute. My default assumption now, after watching dozens of post mortems, is that beyond a certain scale, nobody understands the code in prod. (edited added 2nd para)