AWS S3 HLD: Object Storage That Loses Nothing (Erasure Coding)

"Design S3." At the API it's the simplest system you'll ever draw — PUT key → bytes, GET key → bytes, a hash map the size of the planet. The whole interview lives in one number the API doesn't show: eleven nines of durability. Store ten million objects and you'd expect to lose one — every ten thousand years. And you have to promise that on hardware where a disk dies every few seconds and a datacenter occasionally catches fire. You don't reach eleven nines by buying better disks; you reach it by assuming every disk is already dying and designing so that no single death — not a disk, not a rack,…