Welcome back! We're advancing in our Redis-based backend system project by tackling transactions using pipelines. This enhancement allows us to execute multiple Redis commands as a single atomic operation. You should already be comfortable with managing user data and leaderboards. This unit will optimize these operations using pipelines.

Before we proceed, let's outline the primary focus of this unit. The key tasks include:

1. Adding user data with expiration using pipelines: We will group multiple commands into one pipeline to add user data more efficiently.
2. Adding scores to a leaderboard using pipelines: Using pipelines ensures that these operations are executed atomically.
3. Executing the pipeline: We'll execute the grouped commands within the pipeline as a single operation.

These tasks demonstrate how pipelines can enhance performance and consistency in our Redis operations.

Below is an example of how to implement pipelines in C++ using the hiredis library:

In this code, all commands appended to the pipeline are sent to the Redis server in one batch, which optimizes network usage and ensures atomic execution when redisGetReply() is called.

Let's start building efficient backend systems with this approach!