Redis data model (key-value) - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Redis Key-Value Storage

Which statement best describes how Redis stores data in its key-value model?

A Redis stores data as keys linked exclusively to JSON documents.

B Redis stores data as keys with associated string values only, no other data types.

C Redis stores data only as keys with numeric values for fast calculations.

D Redis stores data as keys associated with various data types like strings, lists, sets, hashes, and sorted sets.

💡 Hint

Think about the flexibility Redis offers beyond simple strings.

Redis supports multiple data types for values, including strings, lists, sets, hashes, and sorted sets, making it versatile for different use cases.

❓ dax_lod_result

intermediate

Calculating Unique Keys in Redis-like Model

Given a Redis-like key-value store where keys represent user IDs and values represent user roles, which DAX measure correctly counts unique user IDs?

Redis

UniqueUsers = DISTINCTCOUNT('UserRoles'[UserID])

A UniqueUsers = SUM('UserRoles'[UserID])

B UniqueUsers = DISTINCTCOUNT('UserRoles'[UserID])

C UniqueUsers = COUNT('UserRoles'[UserID])

D UniqueUsers = COUNTROWS('UserRoles')

💡 Hint

Counting unique keys means counting distinct user IDs.

Using DISTINCTCOUNT counts unique values in the UserID column, which matches counting unique keys.

❓ visualization

advanced

Visualizing Redis Key Expiry Distribution

You have a Redis database with keys that have different expiry times. Which visualization best shows the distribution of key expiry times to help monitor key lifetimes?

A A histogram showing the count of keys grouped by expiry time ranges.

B A line chart showing expiry times on the x-axis and number of keys on the y-axis over time.

C A pie chart showing the percentage of keys per expiry time category.

D A scatter plot showing keys on x-axis and expiry time on y-axis.

💡 Hint

Think about how to show frequency distribution of expiry times.

A histogram groups expiry times into ranges and shows how many keys fall into each range, making it ideal to see distribution.

❓ data_modeling

advanced

Modeling User Sessions in Redis Key-Value Store

You want to model user sessions in Redis using key-value pairs. Each session has a unique session ID, user ID, and expiration time. Which Redis data structure and key design is best for efficient session lookup and expiry?

A Use hash keys with session ID as key and fields for user ID and expiry timestamp, setting Redis key expiry for session timeout.

B Use list keys with session IDs as list elements and separate keys for user IDs and expiry times.

C Use string keys with session ID as key and JSON string as value containing user ID and expiry timestamp.

D Use set keys with user IDs as members and session IDs stored as values in separate keys.

💡 Hint

Consider how Redis expiry works and how to store multiple fields per session.

Hashes allow storing multiple fields per key efficiently, and Redis key expiry can automatically remove sessions after timeout.

🔧 Debug

expert

Identifying Error in Redis Key Expiry Command Usage

Which Redis command usage will cause an error when trying to set a key with expiry?

Options:

A SET mykey "value" EX 60

B SET mykey "value" PX 60000

C SET mykey EXPIRE 60 "value"

D SETEX mykey 60 "value"

💡 Hint

Check the correct syntax for setting expiry with SET command.

Option C uses an invalid syntax 'EXPIRE' inside SET command, which causes an error. The correct syntax uses 'EX' or 'PX' without 'EXPIRE'.