Amazon S3 advertises 11 9’s of durability for both Standard and One Zone-IA object storage classes. This is a mind-bogglingly high level of durability. The way AWS puts it, if you’ve stored 10 million objects, you can expect to lose about one object about every 10,000 years - even within a single availability zone!

It’s important to note, though, that this is the designed durability, not the guaranteed durability. There are all kinds of things that can go wrong that could impact durability on AWS’s side, and it’s even more likely that problems with your application can impact the durability of your data in S3, even if AWS does everything right.

In this talk, we’ll talk about some of those things that might go wrong, and explore what S3’s advertised durability actually means to you if you’re someone who builds systems that use it.