Top-N queries in Redis - Mini Project: Build & Apply

Top-N Queries with Redis Sorted Sets

📖 Scenario: You are managing a leaderboard for a mobile game. Players earn points, and you want to keep track of the top scorers in real-time.

🎯 Goal: Build a Redis sorted set to store player scores, then query the top 3 players with the highest scores.

📋 What You'll Learn

Create a Redis sorted set called game_leaderboard with 5 players and their scores.

Add a new player score to the game_leaderboard.

Query the top 3 players with the highest scores using a Redis command.

Retrieve the scores along with the player names.

💡 Why This Matters

🌍 Real World

Leaderboards in games, ranking systems in apps, or any scenario where you need to keep track of top scores or ratings in real-time.

💼 Career

Understanding Redis sorted sets and top-N queries is valuable for backend developers working on performance-critical applications like gaming, social media, and analytics platforms.

1

Create the initial leaderboard with 5 players

Use the Redis command ZADD game_leaderboard to add these exact players and scores: "Alice" 1500, "Bob" 1200, "Charlie" 1800, "Diana" 1600, "Eve" 1400.

Redis

# Use ZADD to add players and scores to game_leaderboard
# Your code here

Need a hint?

Use ZADD followed by the sorted set name, then pairs of score member.

2

Add a new player score

Add a new player "Frank" with a score of 1700 to the game_leaderboard using the ZADD command.

Redis

ZADD game_leaderboard 1500 Alice 1200 Bob 1800 Charlie 1600 Diana 1400 Eve
# Add Frank with score 1700
# Your code here

Need a hint?

Use ZADD game_leaderboard 1700 Frank to add Frank's score.

3

Query the top 3 players by score

Use the Redis command ZREVRANGE game_leaderboard 0 2 WITHSCORES to get the top 3 players with the highest scores and their scores.

Redis

ZADD game_leaderboard 1500 Alice 1200 Bob 1800 Charlie 1600 Diana 1400 Eve
ZADD game_leaderboard 1700 Frank
# Query top 3 players with scores
# Your code here

Need a hint?

Use ZREVRANGE with 0 2 to get the top 3, and WITHSCORES to include scores.

4

Retrieve and display the top 3 players with their scores

Use the Redis command ZREVRANGE game_leaderboard 0 2 WITHSCORES to retrieve the top 3 players and their scores, completing the leaderboard query.

Redis

ZADD game_leaderboard 1500 Alice 1200 Bob 1800 Charlie 1600 Diana 1400 Eve
ZADD game_leaderboard 1700 Frank
ZREVRANGE game_leaderboard 0 2 WITHSCORES
# Finalize leaderboard query
# Your code here

Need a hint?

This command returns the top 3 players and their scores in descending order.