AWS S3 Versioning

• Versioning in Amazon S3 is a means of keeping multiple variants of an object in the same bucket.
• You can use the S3 Versioning feature to preserve, retrieve, and restore every version of every object stored in your buckets.
• Versioning-enabled buckets can help you recover objects from accidental deletion or overwrite.
• After versioning is enabled for a bucket, if Amazon S3 receives multiple write requests for the same object simultaneously, it stores all of those objects.
• For example, if you delete an object in the S3 versioned enabled bucket, Amazon S3 inserts a delete marker instead of removing the object permanently.
• The delete marker becomes the current object version.

Buckets can be in one of three states:

• Unversioned (the default)
• Versioning-enabled
• Versioning-suspended

How S3 Versioning works

• S3 Versioning keeps multiple versions of an object in one bucket and enables you to restore objects that are accidentally deleted or overwritten.
• For example, if you delete an object, instead of removing it permanently, Amazon S3 inserts a delete marker, which becomes the current object version. You can then restore the previous version.

Version ID

• If you enable versioning for a bucket, Amazon S3 automatically generates a unique version ID for the object that is being stored.
• For example, in one bucket you can have two objects with the same key but different version IDs, such as photo.gif (version 111111) and photo.gif (version 121212).
• If you don’t enable S3 Versioning, Amazon S3 sets the value of the version ID to null. If you enable S3 Versioning, Amazon S3 assigns a version ID value for the object.

Versioning workflows

• When you PUT an object in a versioning-enabled bucket, the current version is overwritten.
• The following figure shows that when a new version photo.gif is PUT into a bucket that already contains an object with the same name, the original object (ID = 111111) remains in the bucket, Amazon S3 generates a new version ID (121212) and adds the newer version to the bucket.

Deleting Object

• When you DELETE an object, all versions remain in the bucket and Amazon S3 inserts a delete marker, as shown in the following figure.

• The delete marker becomes the current version of the object. By default, GET requests retrieve the most recently stored version.
• Performing a simple GET Object request, when the current version is a delete marker, returns a 404 Not Found error, as shown in the above diagram.

• However, you can GET a noncurrent version of an object by specifying its version ID. In the following figure, you GET a specific object version, 111111.

Permanently Delete

• You can permanently delete an object by specifying the version you want to delete.
• Only the owner of an Amazon S3 bucket can permanently delete a version. The following figure shows how DELETE versionId permanently deletes an object from a bucket and that Amazon S3 doesn't insert a delete marker.
• You can add more security by configuring a bucket to enable MFA (multi-factor authentication) delete.
• When you do, the bucket owner must include two forms of authentication in any request to delete a version or change the versioning state of the bucket.