"With the immutable storage, feature blobs will be non-erasable and non-modifiable for a specific retention interval. Now Microsoft announced that this new feature is generally available in all public Azure regions after its preview since June of this year."
Write-Once-Read-Many (WORM)
Technically AWS S3 with versioning enabled also keeps previous versions of data, but semantically this is still different behavior.
Microsoft Azure gains Availability Zones and Immutable Blobs • The Register
