Welcome! In this unit, we will explore how to use Redis streams for event logging. This is an important part of our Redis-based backend system project. By the end of this lesson, you will know how to log events and retrieve them using Redis streams. Remember, you've already learned how to manage user data and handle transactions. Now, we're adding another layer to our system by using streams.

In this unit, we will focus on the following tasks:

1. Adding entries to a stream: We will log user activities in a Redis stream.
2. Reading entries from a stream: You will see how to read the logged events from the stream.

Redis streams are like logs where each entry has a unique ID and can store multiple field-value pairs. They're perfect for event logging.

We start by including the required headers, creating an Asio I/O context, and opening a Boost.Redis connection. We also define the stream name we will use for logging events.

Here, async_run starts the Redis connection in the background. The stream name is "user_activity_stream", which is where our event records will be stored. Each event added to this stream will become part of an ordered log.

Next, we create a Redis request that does three things in one pipeline:

• Adds a login event for Alice
• Adds a login event for Bob
• Reads the first two entries from the stream

XADD writes a new entry to the stream. The * tells Redis to generate a unique ID automatically for each event. Each entry stores field-value pairs such as:

• event = login
• username = alice

Then XREAD reads entries from the stream. The COUNT 2 part limits the result to two entries, and 0-0 means reading from the beginning of the stream. The response type stores two generated IDs as strings and the XREAD result as a generic RESP3 node tree.

Finally, we execute the pipeline, check for errors, print the generated IDs, and show the returned stream data.

async_exec sends all three commands to Redis. If something goes wrong, we print the error and stop the connection.

If the request succeeds:

• The first two response slots contain the IDs returned by the two XADD commands
• The third response slot contains the XREAD result

We print the two generated IDs so you can see the exact entries Redis created. Then we print the raw values from the RESP3 response tree. This gives a simple view of the stream data returned by Redis.

In this code, we use XADD to add two login events to a stream. The * tells Redis to auto-generate unique IDs. We then use XREAD to read back the entries, starting from 0-0 (the beginning) and limiting to 2 entries. The response contains the auto-generated IDs and the stream data as a RESP3 tree structure.

In this lesson, you learned the basic Redis stream workflow for event logging: write events with XADD, then retrieve them with XREAD. This gives your backend a simple way to keep a record of user activity that you can inspect later or process as part of a larger system. In the practice section, you'll use the same pattern yourself, so pay close attention to the stream name, the generated entry IDs, and the field-value pairs stored in each event. These ideas will continue to be useful as the backend grows and starts handling more kinds of activity.