Strong Consistency in S3 and Cloud Block Store

From my armchair in the past few weeks, I have been watching the myriad of announcements at re:Invent by AWS and a few things caught my eye (well a lot of things did, but a few in particular to storage).

The first thing to note was the change in the consistency model in S3. Up until now, consistency was “eventual” within S3 for certain operations like changes to a file, and there are a ton of posts that do a great job of explaining this. One is below:

https://dhruvsharma-50981.medium.com/s3-eventual-data-consistency-model-issues-and-tackling-them-47093365a595

Google “S3 eventual consistency” and you will find tons of examples.

At a high level, when modifying or deleting objects the change may not be immediately reflected. So on an immediate subsequent read, you may not get what you wrote. For busy environments with high change rates/modifications this could lead to corruption. So you needed to understand the behavior and build to or around it.

At re:Invent, AWS announced that strong consistency is now supported for S3 operations:

https://aws.amazon.com/blogs/aws/amazon-s3-update-strong-read-after-write-consistency/

https://aws.amazon.com/s3/consistency/

What you write is what you get. Fantastic!

So what does this have to do with Cloud Block Store? Read on.

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