Redis as cache vs data store vs message broker - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Primary use of Redis as a cache

What is the main reason Redis is used as a cache in applications?

A To store data permanently with complex queries

B To perform heavy data analytics and reporting

C To send messages between different parts of an application

D To temporarily store frequently accessed data for faster retrieval

💡 Hint

Think about why caching helps speed up applications.

Redis as a cache stores data temporarily to speed up access to frequently used information, reducing the need to fetch from slower databases.

🧠 Conceptual

intermediate

Redis as a message broker role

Which Redis feature allows it to act as a message broker?

A Key expiration for automatic data deletion

B Pub/Sub system for sending messages between clients

C Sorted sets for ranking data

D Hashes for storing user profiles

💡 Hint

Message brokers help parts of an app talk to each other.

Redis uses its Pub/Sub feature to send messages between clients, enabling it to work as a message broker.

❓ query_result

advanced

Result of Redis command for cache expiration

What is the output of the following Redis commands?

SET user:1 "Alice" EX 10
TTL user:1

Redis

SET user:1 "Alice" EX 10
TTL user:1

A 0

B -1

C 10

D nil

💡 Hint

EX sets expiration in seconds; TTL returns remaining time.

The SET command with EX 10 sets the key to expire in 10 seconds. TTL returns the remaining time to live, which is 10 seconds immediately after setting.

📝 Syntax

advanced

Correct Redis command to publish a message

Which Redis command correctly publishes the message "Hello" to the channel "news"?

A PUBLISH news Hello

B PUBLISH news "Hello"

C PUBLISH "news" "Hello"

D PUBLISH "news" Hello

💡 Hint

Redis commands do not require quotes for simple strings.

The PUBLISH command syntax is: PUBLISH channel message. Quotes are not needed unless the client requires them, but Redis CLI accepts unquoted simple strings.

🧠 Conceptual

expert

Choosing Redis as data store vs cache

Which scenario best justifies using Redis as a primary data store instead of just a cache?

A Maintaining real-time leaderboard data that must be highly available

B Caching product details that are also stored in a relational database

C Holding temporary API rate limit counters that reset often

D Storing session data that can be lost without issues

💡 Hint

Think about when data loss is unacceptable and fast access is critical.

Using Redis as a primary data store fits scenarios needing fast, reliable access to data that cannot be lost, like real-time leaderboards.