Range queries for scoring in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Retrieve members with scores between 50 and 100

Given a sorted set players with player names as members and their scores as scores, which Redis command returns all players with scores between 50 and 100 inclusive?

Redis

ZADD players 30 "Alice" 60 "Bob" 90 "Charlie" 110 "Diana"

A ZRANGEBYSCORE players 50 100

B ZRANGE players 50 100

C ZREVRANGEBYSCORE players 50 100

D ZRANGEBYSCORE players (50 (100

💡 Hint

Use the command that filters by score range, not by rank.

ZRANGEBYSCORE returns members with scores within the specified range. ZRANGE uses rank indexes, not scores. ZREVRANGEBYSCORE reverses the order but requires the max score first. Parentheses indicate exclusive bounds, so option A excludes 50 and 100.

📝 Syntax

intermediate

Identify the syntax error in this Redis range query

Which option contains a syntax error when trying to get members with scores between 20 and 80 from sorted set scores?

Redis

ZADD scores 10 "x" 30 "y" 70 "z"

A ZRANGEBYSCORE scores 20 80

B ZRANGEBYSCORE scores 20, 80

C ZRANGEBYSCORE scores (20 80

D ZRANGEBYSCORE scores 20 (80

💡 Hint

Check for invalid characters or separators in the command.

Option B uses a comma between scores, which is invalid syntax. Scores must be separated by space only. Options B, C, and D are valid syntax with inclusive or exclusive bounds.

❓ optimization

advanced

Efficiently retrieve top 5 players with scores above 90

You want to get the top 5 players with scores greater than 90 from sorted set leaderboard. Which command is the most efficient and correct?

Redis

ZADD leaderboard 85 "Anna" 92 "Ben" 95 "Cara" 99 "Dave" 100 "Eve" 88 "Fay"

A ZRANGEBYSCORE leaderboard (90 +inf LIMIT 0 5

B ZRANGEBYSCORE leaderboard 90 +inf LIMIT 0 5

C ZREVRANGEBYSCORE leaderboard +inf (90 LIMIT 0 5

D ZREVRANGEBYSCORE leaderboard +inf 90 LIMIT 0 5

💡 Hint

Remember that ZREVRANGEBYSCORE returns members in descending score order.

Option C correctly uses ZREVRANGEBYSCORE with exclusive lower bound (90) and upper bound +inf, limiting to 5 results. Option C uses ZRANGEBYSCORE which returns ascending order, not top scores. Option C includes 90 (not strictly greater). Option C uses inclusive 90, including players with score 90.

🔧 Debug

advanced

Why does this range query return no results?

You run the command ZRANGEBYSCORE games 100 50 on a sorted set games with scores from 10 to 150, but get an empty list. Why?

Redis

ZADD games 10 "g1" 50 "g2" 100 "g3" 150 "g4"

A ZRANGEBYSCORE only works with integer scores

B ZRANGEBYSCORE requires the max score first, then min score

C The sorted set is empty, so no results

D The min score is greater than max score; range is invalid

💡 Hint

Check the order of min and max scores in the command.

ZRANGEBYSCORE expects min score first, then max score. Here min=100 and max=50 is invalid, so no members match. Option D is incorrect because min must come first. The set is not empty, and scores can be floats.

🧠 Conceptual

expert

Understanding exclusive and inclusive bounds in Redis range queries

Which option correctly describes the difference between ZRANGEBYSCORE key (50 100 and ZRANGEBYSCORE key 50 (100?

A The first excludes 50 but includes 100; the second includes 50 but excludes 100

B Both exclude 50 and 100

C The first includes 50 and excludes 100; the second excludes 50 and includes 100

D Both include 50 and 100

💡 Hint

Parentheses before a score mean exclusive bound for that score.

In Redis, a parenthesis before a score means exclusive. So (50 excludes 50, 50 includes it. The first command excludes 50 but includes 100. The second includes 50 but excludes 100.