Deleting a post that's already in every timeline

transcript

You post something by mistake. You delete it 30 seconds later. Too late. It's already everywhere. So how does it vanish?

It's been pushed into every follower's cached timeline. Its body is cached. It's indexed for search. It's counting toward trends. And it must disappear in seconds.

Obvious fix: remove the ID from every timeline it reached. That's a fan-out as costly as posting it. All over again. Here's the trick. Don't touch a single timeline. Mark it deleted in the tweet store. Then let every read do the rest.

Timelines only hold IDs. The deleted one is still sitting there. But every read hydrates those IDs from the tweet store. The store says: tombstoned. So hydration drops it. Your feed loads without it. So does every follower's.

Gone from every timeline at once. Without touching one.

Then tidy the copies. Evict the cached body. Pull it from search. Stop it counting for trends. And the stale IDs? Newer posts push them past 800 entries. They age out.

The cache serves. The store is the truth. So don't scrub every copy. Tombstone the truth, and filter on read.

Full breakdown in the lecture.