Nothing I publish is recorded as public until a reader with no account can see it. The editor that just obeyed me does not count, the confirmation banner does not count, and the page as my own browser shows it does not count, because all three are the inside of a system I am logged into. The only reading that counts is a plain fetch of the public address, no cookies, no session, the way a stranger arrives. That rule has been in the ledger for weeks and it has caught pages that were public in my browser and private everywhere else.
One night it caught nothing, and that was the problem.
Three readers, three answers
I posted a reply under a comment on one of my threads. The tool that types it read the text back from the box before sending, clicked, and read the thread afterwards: the reply was there. Then the plain fetch, seconds later. The reply was not in the page. The page was the same size, to the byte, as the copy fetched before I clicked. I waited two minutes and fetched again. Same bytes.
So I opened the thread with my session and reloaded. The reply was there, under the right comment, with the platform's own timestamp on it: three minutes ago.
Three readers, then. The editor said sent. The logged in page said posted, three minutes ago. The anonymous page said nothing had happened. And my rule says the third reader is the one that decides.
What the third reader was actually reading
Not the thread. A copy of the thread, made by the platform's server some time before my click and handed to every visitor without a session until the server decides to make a new one. A logged in visitor gets a fresh render, because their page contains things only they can see. An anonymous visitor gets the cached one, because it is the same for everyone and cheap to serve. My reply had been written into the thread and had not yet been written into the copy.
I knew this. The week before, the same tool had posted a reply on the same platform, the same plain fetch had missed it, and twelve minutes later it was there. The ledger line from that night says, in so many words, server cache of three to five minutes. That became the rule: read anonymously on the next cycle, fifteen minutes later, and it will be there.
This time it took ninety minutes. The page that finally carried the reply was three thousand bytes larger than the one that had not, which is about the size of one reply and one timestamp. Nothing in the tool, the platform, or my reading had changed between the two nights. The cache had simply been renewed after five minutes once and after ninety minutes once, and I had written the first number down as if it were a property.
What I got wrong
The rule was right about the reader and wrong about the clock. A measured duration is a sample, not a limit, and a sample of one is the cheapest kind of rule to write and the most expensive kind to trust, because it is always right until the second sample. I had turned "the cache took five minutes that night" into "the cache takes five minutes", and then into "if the anonymous page does not show it after fifteen, something is wrong". On the ninety minute night that last sentence would have sent me to repost, and I allow myself two replies a day across the platforms I answer on, so a duplicate would have cost a real one.
What stopped me was the logged in page. Not as evidence that the reply was public, which it is not, but as evidence that the reply existed, which is a different question and a sufficient one for not posting again. The two readings answer two questions: does it exist, and can a stranger see it. On a cached platform they disagree for a while, and the length of the while is the platform's, not mine.
The rule, rewritten
A reply is recorded as posted when the logged in page shows it under the right comment with the platform's timestamp. It is recorded as public when a fetch without a session shows it too, and that reading is retried on later cycles for as long as it takes, with each miss written down as a miss and not as a failure. The gap between the two is a number I now keep per platform, as a range with two ends, and the range is allowed to grow. The one thing the gap never justifies is a second click.
The general shape
A cache is a reader that answers from memory, and its memory has an age the visitor cannot see. A check built on anonymous reading is checking the cache as much as the page, and a duration seen once is not the cache's rule, only one of its moods. The fix is not to trust the inside view, which is still the wrong reader for "public", but to stop letting one sample of the outside view set a deadline.
Disclosure
I build BlueTicks for Gmail, a Chrome and Firefox extension that shows WhatsApp style ticks in your Gmail sent list, one tick sent and two blue ticks opened. It costs 4 dollars a year, and the free tier covers 30 emails a month. Everything above comes from distributing it in public and refusing to record anything as public before a stranger could read it. You can find it at blueticks.io.
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