ZSCORE for member score in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of ZSCORE for an existing member?

Given a sorted set named players with members and their scores, what will be the output of ZSCORE players "Alice" if Alice's score is 1500?

Redis

ZADD players 1500 Alice
ZSCORE players "Alice"

A "1500"

B Error: member not found

C nil

D 1500

💡 Hint

Remember that ZSCORE returns the score as a string if the member exists.

The ZSCORE command returns the score of the specified member as a string if the member exists in the sorted set. If the member does not exist, it returns nil.

❓ query_result

intermediate

What does ZSCORE return for a non-existing member?

If you run ZSCORE players "Bob" but Bob is not in the sorted set, what will Redis return?

Redis

ZADD players 1500 Alice
ZSCORE players "Bob"

A nil

B ""

C Error: member not found

D "0"

💡 Hint

Think about what Redis returns when a member is missing in a sorted set.

When the member does not exist in the sorted set, ZSCORE returns nil to indicate absence.

🧠 Conceptual

advanced

Why does ZSCORE return scores as strings?

Which reason best explains why Redis returns the score as a string when using ZSCORE?

A Because Redis converts scores to integers before returning them.

B Because Redis stores all data internally as strings for consistency and network transmission.

C Because Redis uses JSON format for all responses.

D Because Redis only supports string members, not numeric scores.

💡 Hint

Think about how Redis handles data types and communication.

Redis stores and transmits data as strings to keep things simple and fast. Even numeric scores are sent as strings.

📝 Syntax

advanced

Which ZSCORE command syntax is correct?

Choose the correct syntax to get the score of member "Charlie" from sorted set "game_scores".

A ZSCORE game_scores Charlie

B ZSCORE "game_scores" "Charlie"

C ZSCORE "game_scores" Charlie

D ZSCORE game_scores "Charlie"

💡 Hint

Member names with special characters or spaces need quotes.

The correct syntax requires the sorted set name without quotes and the member name in quotes if it contains special characters or to be safe.

❓ optimization

expert

How to efficiently check scores of multiple members?

You want to get scores for multiple members in a sorted set efficiently. Which approach is best?

A Run ZSCORE command separately for each member one by one.

B Use ZRANGE with WITHSCORES and filter results client-side.

C Use a Lua script to batch ZSCORE calls in Redis server.

D Use ZSCORE with multiple members in one command.

💡 Hint

Think about reducing network round-trips and server load.

Redis does not support multiple members in one ZSCORE command. Running many commands separately causes many network calls. Using a Lua script batches calls inside Redis, reducing network overhead and improving performance.