You need to store large binary files (up to 2 GB) that are frequently overwritten in place (entire file replaced). You want to minimize storage cost and write latency. Which Azure Blob Storage type should you use?
Block Blobs allow you to upload large files in blocks and replace the entire blob by committing a new block list, providing low latency and cost efficiency.
Why this answer
Block blobs are optimized for storing large binary files (up to ~4.75 TB) and support high-throughput uploads via PutBlock and PutBlockList operations. They allow overwriting an entire blob by uploading a new set of blocks, which minimizes write latency compared to page blobs that require sector-aligned writes. Block blobs also offer lower storage cost than page blobs, making them the best choice for frequently overwritten large files.
Exam trap
The trap here is that candidates often confuse 'frequently overwritten' with 'random access' and choose Page Blob, forgetting that page blobs are optimized for small, random writes (like VHDs) and are more expensive, while block blobs are the correct choice for large file replacement with low latency and cost.
How to eliminate wrong answers
Option B (Page Blob) is wrong because page blobs are designed for random read/write access in 512-byte pages (e.g., VHDs for Azure VMs) and have higher storage costs and write latency due to sector alignment requirements, making them suboptimal for large file overwrites. Option C (Append Blob) is wrong because append blobs only support appending data to the end of the blob and do not allow overwriting existing content in place. Option D (Archive Blob) is wrong because archive blobs are for cold data with infrequent access, have high read latency (hours to rehydrate), and are not designed for frequent overwrites.