Is the Azure Put Blob operation atomic?

Question

The documentation for Azure's Put Blob REST API operation tells us that it is possible to upload a block blob up to 64 MB with a single request.

I'm wondering whether such an operation is atomic. In particular I need to know whether the following assumptions are true or false.

1. If two or more clients concurrently to put a particular non-existing blob using this API specifying If-None-Match: *, then at most one of them will succeed.

2. A blob put using this API will never be partially exposed. It will either not exist or exist with the entire content that was put (<64MB) including metadata.

Can anyone confirm or refute these assumptions?

Answer 1

I have received confirmation directly from a Microsoft support technician that both of these assumptions are true:

1. If two or more clients concurrently to put a particular non-existing blob using this API specifying If-None-Match: *, then at most one of them will succeed.

2. A blob put using this API will never be partially exposed. It will either not exist or exist with the entire content that was put (<64MB) including metadata.