The 404 only we could see: 23.8 hours inside a cache entry we made ourselves

For 23.8 hours, one of our published articles returned 404 to us and 200 to everyone else. The article was fine. Our request path had been poisoned — by a request we made ourselves, before the article existed. Here is the whole failure, including the second defect that made a one-article problem look like a forty-four-article blackout. What we saw...