AWS S3: never lose one of 500 trillion

How S3 keeps 500 trillion+ objects at 11 nines of durability and 200M+ requests a second: a partitioned index kept apart from 10 + 6 erasure-coded bytes spread across three AZs, fast repair, a witness check that makes every read see the latest write, prefix partitions that split on load, and versioning and Object Lock for the deletes durability can't stop.