Message queue concept in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of a message queue in system design?

Choose the best description of why message queues are used in distributed systems.

A To store large files for long-term archival in the system.

B To directly connect two components for synchronous data exchange.

C To enable asynchronous communication between components by storing messages temporarily.

D To replace databases for storing user data permanently.

💡 Hint

Think about how systems handle tasks that don't need immediate response.

Message queues allow components to send messages without waiting for immediate processing, enabling asynchronous communication and decoupling.

❓ Architecture

intermediate

Which component is responsible for ensuring message durability in a message queue system?

Identify the part of a message queue system that guarantees messages are not lost even if the system crashes.

A Message broker's persistent storage mechanism.

B Client application sending the message.

C Network protocol used for message transmission.

D Consumer application processing the message.

💡 Hint

Consider where messages are saved to survive failures.

The message broker uses persistent storage (like disk) to save messages so they survive crashes and restarts.

❓ scaling

advanced

How can a message queue system handle very high message throughput without losing messages?

Choose the best approach to scale a message queue system to handle millions of messages per second reliably.

A Use a single queue with a very large memory buffer only.

B Partition the queue into multiple shards and distribute messages across them.

C Increase the number of consumers but keep one queue shard.

D Store messages only in memory to speed up processing.

💡 Hint

Think about dividing work to avoid bottlenecks.

Partitioning the queue into shards allows parallel processing and avoids single points of congestion, improving throughput and reliability.

❓ tradeoff

advanced

What is a key tradeoff when choosing between at-least-once and exactly-once message delivery in a queue system?

Select the correct tradeoff between these two delivery guarantees.

A At-least-once may cause duplicate messages; exactly-once requires more complex coordination and overhead.

B At-least-once is slower; exactly-once is always faster and simpler.

C At-least-once guarantees no duplicates; exactly-once may lose messages.

D At-least-once requires distributed transactions; exactly-once does not.

💡 Hint

Consider the complexity and message duplication risks.

At-least-once delivery can lead to duplicates but is simpler; exactly-once avoids duplicates but needs complex coordination like idempotency or transactions.

❓ estimation

expert

Estimate the storage needed for a message queue system that handles 10 million messages per hour, each averaging 1 KB, with a retention period of 7 days.

Calculate the approximate disk storage required to retain all messages for 7 days.

A Approximately 1680 GB

B Approximately 168 GB

C Approximately 16.8 TB

D Approximately 1.68 TB

💡 Hint

Calculate total messages in 7 days and multiply by message size.

10 million messages/hour × 24 hours × 7 days = 1.68 billion messages. Each 1 KB means 1.68 TB storage needed.