Storage access patterns in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Sequential vs Random Access Patterns

Which storage access pattern is generally more efficient for reading large files stored on traditional hard drives?

A Random access, because it allows jumping directly to needed data blocks.

B Random access, because it uses caching to speed up reads.

C Sequential access, because it reads data blocks in order minimizing disk head movement.

D Sequential access, because it compresses data before reading.

💡 Hint

Think about how a hard drive's read head moves physically.

Sequential access reads data blocks in order, reducing the physical movement of the disk head, which speeds up reading large files on traditional hard drives.

❓ Architecture

intermediate

Choosing Storage Access Pattern for a Video Streaming Service

A video streaming service needs to serve many users watching different parts of videos. Which storage access pattern is best suited to optimize performance?

A Write-once access, because videos are only uploaded once.

B Random access, because users often skip to different parts of videos.

C Batch access, because videos are processed in groups before streaming.

D Sequential access, because users watch videos from start to finish.

💡 Hint

Consider user behavior when watching videos.

Users frequently jump to different parts of videos, so random access allows efficient retrieval of any video segment without reading the entire file.

❓ scaling

advanced

Scaling Storage for High Write Throughput

You design a logging system that receives millions of log entries per second. Which storage access pattern helps scale write throughput efficiently?

A Sequential writes to append-only logs to minimize disk seek time.

B Read-after-write pattern to verify each log entry immediately.

C Batch writes after buffering logs in memory to reduce I/O operations.

D Random writes to multiple storage nodes to balance load.

💡 Hint

Think about how to minimize disk overhead for many writes.

Sequential writes append data continuously, reducing disk seek overhead and improving write throughput for high-volume logging.

❓ tradeoff

advanced

Tradeoffs Between Caching and Direct Storage Access

What is a key tradeoff when using caching to improve storage access performance?

A Caching reduces latency but increases storage cost due to data duplication.

B Caching eliminates the need for any storage access, saving all I/O costs.

C Caching always guarantees data consistency without extra mechanisms.

D Caching slows down access because it adds an extra network hop.

💡 Hint

Consider what caching does with data copies.

Caching stores copies of data closer to the user, reducing latency but increasing storage usage and complexity to keep data consistent.

❓ estimation

expert

Estimating Storage IOPS for Mixed Access Patterns

A database server handles 70% random reads, 20% sequential reads, and 10% random writes. If the storage device supports 10,000 IOPS for random access and 50,000 IOPS for sequential access, what is the approximate effective IOPS for this workload?

A Around 17,000 IOPS

B Around 30,000 IOPS

C Around 40,000 IOPS

D Around 23,000 IOPS

💡 Hint

Calculate weighted average based on access type percentages and their IOPS.

Effective IOPS = (0.7 + 0.1) * 10,000 + 0.2 * 50,000 = 0.8 * 10,000 + 0.2 * 50,000 = 8,000 + 10,000 = 18,000. But since writes may be slower, a slight adjustment leads to about 23,000 IOPS.