Blob storage (S3, Azure Blob) in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Architecture

intermediate

Choosing the right storage tier for cost optimization

You have a blob storage bucket that stores user-uploaded photos. Most photos are accessed frequently for the first week, then rarely afterwards. Which storage tier choice best balances cost and access speed?

A Store photos in the hot tier for the first week, then move them to the cool or archive tier.

B Store photos in the cool tier immediately after upload to save cost.

C Store all photos in the hot tier to ensure fast access at all times.

D Store photos in the archive tier immediately to minimize storage cost.

💡 Hint

Think about how access frequency changes over time and how storage tiers differ in cost and speed.

The hot tier is optimized for frequent access but costs more. The cool and archive tiers cost less but have slower access. Moving photos after one week balances cost and performance.

❓ service_behavior

intermediate

Understanding eventual consistency in S3

You overwrite an existing file in an Amazon S3 bucket and immediately try to read it from another client. Sometimes the old version is returned. What explains this behavior?

A S3 uses eventual consistency for read-after-write of new objects in all regions.

B S3 uses eventual consistency for overwrite PUTs and DELETEs, but read-after-write consistency for new objects in most regions.

C S3 provides read-after-write consistency for new objects in all regions, so this should never happen.

D S3 requires manual replication to make new objects visible to all clients.

💡 Hint

Consider the difference between new object creation and overwriting existing objects.

S3 provides read-after-write consistency for new objects in most regions, but eventual consistency for overwrites and deletes.

❓ security

advanced

Securing Azure Blob Storage with least privilege

You want to allow an application to upload files to a specific container in Azure Blob Storage without giving full storage account access. Which approach follows the least privilege principle?

A Generate a shared access signature (SAS) token scoped to the container with write permissions and limited expiry time.

B Share the storage account access key with the application for full access.

C Make the container public so the application can upload files without authentication.

D Assign the Storage Blob Data Contributor role at the storage account level to the application identity.

💡 Hint

Think about granting only the permissions needed and for a limited time.

A SAS token scoped to the container with write permission and expiry limits access to only what the app needs, following least privilege.

❓ Configuration

advanced

Configuring S3 bucket for static website hosting

You want to host a static website using an Amazon S3 bucket. Which configuration is required to serve the website correctly?

A Set the bucket policy to deny all public access.

B Enable versioning on the bucket and upload an index.html file.

C Enable static website hosting on the bucket and set the index document name.

D Create a lifecycle rule to archive old website files.

💡 Hint

Think about what S3 needs to serve files as a website.

Enabling static website hosting and specifying the index document allows S3 to serve the website content properly.

✅ Best Practice

expert

Designing multi-region disaster recovery for blob storage

Your company requires a disaster recovery plan for blob storage that ensures data durability and availability even if one cloud region fails. Which design best meets this requirement?

A Manually copy blobs daily from the primary region to a secondary region using scripts.

B Store data only in one region and rely on backups stored on-premises.

C Use locally redundant storage (LRS) to keep multiple copies within the same region.

D Use geo-redundant storage (GRS) or read-access geo-redundant storage (RA-GRS) to replicate data asynchronously to a secondary region.

💡 Hint

Consider built-in replication options that provide automatic failover or read access.

GRS and RA-GRS replicate data asynchronously to a secondary region, providing durability and availability during regional outages.