Why Do I Always See My Uploads in S3 Immediately?

When uploading larger files, S3 uses multi-part uploads, breaking down the file for faster processing. This could help explain why you see your uploads immediately. They incorporate complex algorithms for efficiency, which you can read more about in detail in my blog on Substack. Understanding these mechanisms can truly enhance your grasp of how S3 functions!

It's not so much a question of 'why' but rather how S3 is designed. It operates under a principle called Strong Consistency, which ensures that once a file is uploaded, an immediate GET will always reflect that upload. This is a key feature that prevents issues seen in systems with eventual consistency, where changes might not be reflected instantly due to delays in replication across servers.

Your question seems to touch on how S3 achieves strong read-after-write consistency, which is definitely the design you want in a storage service. The details on that are quite technical but you can find out more on AWS's site about how they manage consistency across their services. Check out the [AWS documentation on consistency](https://aws.amazon.com/s3/consistency/) for in-depth details.

The immediate visibility of an upload in S3 is expected behavior. After you upload a file, any attempt to retrieve it should show its current state. If it didn't, it would create confusion and be counterproductive to how users expect file handling to work. I think there are nuances though, especially when dealing with larger files or overwrites.

I think the 'why' boils down to the difficulties of handling eventual consistency in applications. When it comes to S3, they built systems to make sure that users always see their uploads immediately, removing the pain of managing such consistency in your applications.