Welcome to the next exciting part of our Redis-based backend system project. In this unit, we will focus on building leaderboard functionality using Redis's sorted sets. Building a leaderboard is a popular use case for many applications, such as games and competitive platforms. You’ve got a good handle on managing user data from previous lessons, so let’s build on that foundation.

In this unit, we will work on three main tasks:

1. Adding user scores to a leaderboard: Use Redis's sorted sets to store user scores efficiently.
2. Retrieving the leaderboard: Fetch and display the top users along with their scores.
3. Getting a user's rank and score: Retrieve a specific user's ranking and score from the leaderboard.

These tasks will demonstrate how Redis sorted sets help maintain order and provide efficient rank-based queries.

To add user scores to a leaderboard, we’ll use Redis’s zadd command. In Java, the zadd method of Jedis allows us to add a user with an associated score to a sorted set. Here’s the relevant portion of the User class:

This method adds the user’s score to the "leaderboard" sorted set. As a reminder, pipelines allow multiple commands to be sent in one go, improving performance by reducing network latency.