100 Days of AWS – Day 16

 

100 Days of AWS – Day 16: Never Lose a File Again with S3 Versioning

Welcome to Day 17! Today, we're talking about a feature that can save you from one of the most common IT disasters: accidental data loss caused by human error. Let's dive into the powerful data protection capabilities of S3 Versioning.

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The Question

A developer accidentally uploads an incorrect version of a critical configuration file to an S3 bucket, overwriting the correct one. To easily recover the previous, correct version of the file, which S3 feature should have been enabled on the bucket before the accident?

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The Correct Answer

The correct answer is (C) S3 Versioning.

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Why It's Correct: A Time Machine for Your Objects

S3 Versioning is a bucket-level setting that, once enabled, keeps a complete history of all versions of an object. It protects you against both accidental overwrites and deletions.

Here's how it works:

• On Overwrite: When you upload a new file with the same name, S3 doesn't actually erase the old one. It simply keeps the old file as a "previous version" and makes your newly uploaded file the "current version."
• On Delete: When you delete a file from a versioned bucket, S3 doesn't permanently remove it. Instead, it places a special "delete marker" on the object. This delete marker becomes the current version, effectively hiding the object, but the old data is still there.

This means you can "undelete" a file by simply removing the delete marker, or roll back to a previous version by deleting the current one.

An Analogy: Google Docs History

Think of S3 Versioning like the version history in Google Docs. Every change is saved, and if you make a mistake, you can instantly revert to an older, correct version. A bucket without versioning is like a simple text file on your desktop; once you overwrite it, the previous data is gone for good.

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Analysis of the Incorrect Options

• (A) S3 Lifecycle Policies: These are rules for cost management. For example, you can create a rule to "delete previous versions after 365 days" to save space, but the policy itself doesn't enable the versioning history.
• (B) S3 Replication: This feature (CRR/SRR) automatically copies objects to another bucket, usually in a different region. It's a tool for disaster recovery and redundancy, not for recovering from an overwrite within the same bucket.
• (D) S3 Bucket Policies: These are JSON-based policies used to manage permissions and control access to your S3 bucket. They are a core part of S3 security, not data recovery.