ZINCRBY for score updates in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the new score of 'player1' after this command?

Given a sorted set 'game_scores' with 'player1' having a score of 50, what will be the score of 'player1' after running:

ZINCRBY game_scores 20 player1

Redis

ZINCRBY game_scores 20 player1

A 70

B 20

C 50

D Error: member not found

💡 Hint

ZINCRBY adds the increment to the current score of the member.

ZINCRBY increases the score of 'player1' by 20. Since the original score was 50, the new score is 70.

❓ query_result

intermediate

What happens if the member does not exist?

What will be the result of running:

ZINCRBY game_scores 15 playerX

when 'playerX' is not in the sorted set 'game_scores'?

Redis

ZINCRBY game_scores 15 playerX

A 0

B Error: member not found

C No change, returns nil

D 15

💡 Hint

ZINCRBY adds the member if it does not exist, starting with the increment as score.

If the member does not exist, ZINCRBY adds it with the increment as its score, so the score becomes 15.

📝 Syntax

advanced

Which command syntax is correct to increase 'player2' score by 10?

Choose the correct Redis command to increase the score of 'player2' by 10 in the sorted set 'game_scores'.

A ZINCRBY game_scores player2 10

B ZINCRBY 10 game_scores player2

C ZINCRBY game_scores 10 player2

D ZINCRBY player2 game_scores 10

💡 Hint

The syntax is ZINCRBY key increment member.

The correct syntax is ZINCRBY followed by the key, then the increment, then the member name.

❓ optimization

advanced

How to efficiently update multiple player scores?

You want to increase scores of multiple players in 'game_scores' by different amounts. Which approach is best for performance?

A Use a Redis pipeline to send multiple ZINCRBY commands at once.

B Run multiple ZINCRBY commands one by one.

C Use ZINCRBY with multiple members in one command.

D Delete and recreate the sorted set with updated scores.

💡 Hint

Pipelining reduces network round trips.

Redis pipelines allow sending multiple commands in one go, reducing latency and improving performance.

🧠 Conceptual

expert

What is the effect of using a negative increment with ZINCRBY?

If you run:

ZINCRBY game_scores -30 player3

and 'player3' has a current score of 25, what will be the new score and what happens if the score becomes negative?

A Member is removed if score goes below zero.

B New score is -5; Redis allows negative scores in sorted sets.

C Error; Redis does not allow negative increments.

D New score is 0; Redis sets negative scores to zero automatically.

💡 Hint

Redis sorted sets can have negative scores.

ZINCRBY allows negative increments and scores can be negative; Redis does not remove members or clamp scores automatically.