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

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a key with an expiration time in Redis.

Redis

SET mykey myvalue EX [1]

Drag options to blanks, or click blank then click option'

A60

Bmyvalue

CGET

DDEL

Attempts:

3 left

💡 Hint

Common Mistakes

Using a command name instead of a number for expiration.

Omitting the expiration time.

The EX option sets the expiration time in seconds. Here, 60 means the key expires after 60 seconds.

2fill in blank

medium

Complete the code to retrieve the value of a key in Redis.

Redis

[1] mykey

Drag options to blanks, or click blank then click option'

AEXPIRE

BDEL

CSET

DGET

Attempts:

3 left

💡 Hint

Common Mistakes

Using SET instead of GET.

Using DEL which deletes the key.

The GET command retrieves the value stored at the specified key.

3fill in blank

hard

Fix the error in the code to publish a message to a Redis channel.

Redis

PUBLISH [1] "Hello World"

Drag options to blanks, or click blank then click option'

AGET

Bmykey

Cmychannel

DSET

Attempts:

3 left

💡 Hint

Common Mistakes

Using a key name instead of a channel name.

Using a command name instead of a channel.

The PUBLISH command sends a message to a channel. The channel name should be a string like mychannel.

4fill in blank

hard

Fill both blanks to create a Redis hash and set a field value.

Redis

HSET [1] [2] "John"

Drag options to blanks, or click blank then click option'

Auser:1000

Bname

Cage

Dmykey

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the hash key and field.

Using a simple key instead of a hash key.

HSET sets a field in a hash. The first blank is the hash key, like user:1000. The second blank is the field name, like name.

5fill in blank

hard

Fill all three blanks to subscribe to a Redis channel and receive messages.

Redis

SUBSCRIBE [1] [2] [3]

Drag options to blanks, or click blank then click option'

Anews

Bupdates

Calerts

Dmykey

Attempts:

3 left

💡 Hint

Common Mistakes

Including a key name instead of a channel.

Using commands instead of channel names.

The SUBSCRIBE command listens to one or more channels. Here, the blanks are channel names like news, updates, and alerts.

Practice

1. Which of the following best describes Redis when used as a cache?

easy

A. It sends messages between different parts of an app.

B. It permanently stores large amounts of data for apps.

C. It temporarily stores data to speed up app responses.

D. It analyzes data to find patterns automatically.

Solution

1. Step 1: Understand Redis cache role

   Redis cache stores data temporarily to help apps respond faster by avoiding repeated data fetching.

2. Step 2: Compare other roles

   Permanent storage is data store, messaging is message broker, and analysis is not Redis's main role.

3. Final Answer:

   It temporarily stores data to speed up app responses. -> Option C

4. Quick Check:

   Cache = Temporary fast storage [OK]

Hint: Cache means temporary fast storage to speed apps [OK]

Common Mistakes:

• Confusing cache with permanent data store
• Thinking Redis analyzes data automatically
• Mixing message broker role with cache

2. Which Redis command is used to publish a message to a channel when Redis acts as a message broker?

easy

A. SET

B. PUBLISH

C. GET

D. SUBSCRIBE

Solution

1. Step 1: Identify publish command in Redis

   The PUBLISH command sends a message to subscribers on a channel in Redis's message broker role.

2. Step 2: Differentiate from other commands

   SET stores data, GET retrieves data, SUBSCRIBE listens to messages but does not send them.

3. Final Answer:

   PUBLISH -> Option B

4. Quick Check:

   Send message = PUBLISH [OK]

Hint: Publish sends messages; subscribe listens [OK]

Common Mistakes:

• Using SET or GET to send messages
• Confusing SUBSCRIBE with PUBLISH
• Thinking GET publishes messages

3. Consider this Redis usage: You store user session data with expiration times to speed up login checks. What role is Redis playing here?

medium

A. Cache

B. Message broker

C. Data store

D. Analytics engine

Solution

1. Step 1: Analyze session data with expiration

   Storing data with expiration to speed up access fits caching, as data is temporary and speeds up app.

2. Step 2: Exclude other roles

   Message broker sends messages, data store keeps permanent data, analytics engine is unrelated.

3. Final Answer:

   Cache -> Option A

4. Quick Check:

   Temporary session data = Cache [OK]

Hint: Temporary data with expiry means cache [OK]

Common Mistakes:

• Thinking session data is permanent storage
• Confusing message broker with cache
• Assuming analytics role for session data

4. You wrote this Redis command to send a message: SUBSCRIBE news. What is wrong if your goal was to send a message?

medium

A. SUBSCRIBE deletes the channel.

B. SUBSCRIBE command syntax is incorrect.

C. SUBSCRIBE stores messages permanently.

D. SUBSCRIBE is for receiving messages, not sending.

Solution

1. Step 1: Understand SUBSCRIBE command purpose

   SUBSCRIBE listens to messages on a channel; it does not send messages.

2. Step 2: Identify correct sending command

   To send messages, use PUBLISH, not SUBSCRIBE.

3. Final Answer:

   SUBSCRIBE is for receiving messages, not sending. -> Option D

4. Quick Check:

   SUBSCRIBE = receive, PUBLISH = send [OK]

Hint: Subscribe listens; publish sends messages [OK]

Common Mistakes:

• Using SUBSCRIBE to send messages
• Thinking SUBSCRIBE deletes channels
• Believing SUBSCRIBE stores messages

5. You want to use Redis to both speed up data access and send notifications between app parts. Which setup correctly uses Redis roles?

hard

A. Use Redis as a cache for data and use PUBLISH/SUBSCRIBE for messaging.

B. Use Redis only as a data store and ignore messaging features.

C. Use Redis as a message broker only, not for caching.

D. Use Redis to permanently store messages and cache data simultaneously.

Solution

1. Step 1: Identify Redis roles for caching and messaging

   Redis can cache data to speed access and use PUBLISH/SUBSCRIBE commands to send messages between app parts.

2. Step 2: Exclude incorrect setups

   Ignoring messaging misses notification need; message broker only misses caching; permanent message storage is not typical.

3. Final Answer:

   Use Redis as a cache for data and use PUBLISH/SUBSCRIBE for messaging. -> Option A

4. Quick Check:

   Cache + Pub/Sub = correct multi-role use [OK]

Hint: Combine cache and pub/sub for speed and messaging [OK]

Common Mistakes:

• Using Redis only for one role when multiple needed
• Trying to store messages permanently in Redis
• Ignoring pub/sub for notifications