A media app uploads camera files of around 10 GB each over unreliable mobile networks. After a dropped connection, the upload should continue from the last successful chunk rather than starting over. Which client technique should be used?
Show answer and explanation
Answer: A
Block blobs accept chunks as uncommitted blocks, each identified by an ID. A failed chunk can be retried alone, and the blocks already uploaded are kept, so the transfer resumes from the last successful point. Only when every block is present does the client commit the block list, which makes the whole file visible at once. This is the standard resumable upload pattern for large blobs.
Why the other options are wrong
- B. A single request must restart completely after a dropped connection, and a long timeout does not help when the network fails mid-transfer, so resumption is impossible.
- C. Azure Files is a different service with its own protocols, and copy-on-write over SMB does not provide the block-level resumption that blob uploads use for large files.
- D. Compression might reduce the size of camera files a little, but a single request still fails and restarts from zero if the connection drops, so resumability is not addressed.