I'm trying to understand something I encountered during a test about Amazon S3. The question was: "If you PUT a new object into S3 and immediately GET it, will you always see your upload? What about if you overwrite an existing object?" I initially answered that S3 is just designed that way, but I failed because my answer didn't feel robust enough. I really want to know why this immediate visibility of uploads happens. Can anyone explain the reasoning behind it?
4 Answers
To put it simply, handling eventual consistency at the application layer can get really messy. In fact, this type of strong consistency is a newer feature of S3. Before, there were situations where an upload might not immediately be visible, which could lead to chaos in your applications. For developers, knowing the object will be ready right after upload is a huge relief!
S3 provides strong read-after-write consistency, which means that once you upload an object, you can immediately retrieve it. This predictable behavior is what we expect from a file management system, as it ensures data integrity. Otherwise, it would be confusing if you couldn't see your uploads right away! If you're looking for the technical details, AWS has a page that'll help explain that consistency model further: https://aws.amazon.com/s3/consistency/
Thanks for the link! I appreciate the clear explanation, I'm just trying to wrap my head around the finer details.
Honestly, the expected behavior is that you can see your uploads right away. If you didn't see your uploaded content immediately, it would lead to a lot of confusion. That's why it's such a key aspect of how systems like S3 are built. Intuitively, we just want things to work!
Exactly! I'm glad we agree on that.
I think your core confusion is about how S3 manages uploads, especially with large files. S3 uses a feature called multipart uploads, allowing big objects to be broken down and uploaded in pieces, which can then be retrieved immediately once the final object is assembled. This efficient method contributes to the strong consistency model.
That makes a lot of sense! Thanks for breaking it down for me.
I see what you mean, that sounds really complicated. Thanks for clarifying!