Welcome back! Previously, you learned how to build and execute basic transactions in Redis using pipelines in C++. In this lesson, we are going a step further by introducing the concept of monitoring keys to control transaction execution. This approach is essential for scenarios where you need to ensure operations are completed only when specific conditions are met.

Let's take a look at how you can implement key monitoring alongside transaction handling in your code using hiredis.

Here are detailed explanations for the key Redis commands used for transactions and key monitoring:

• Atomicity means all operations within a transaction are completed successfully or none at all. This property prevents inconsistencies that may arise from partial updates.
• For instance, in our code, if another client updates the balance while our transaction is pending, the entire operation will abort, ensuring we don't apply changes on outdated data. The updateBalance function keeps retrying until the transaction is successfully applied without other interferences.

In this lesson, you learned how to monitor a key with the watch command in Redis using hiredis in C++. The above code ensures that if another client modifies the key being monitored, the transaction is retried until it successfully updates the balance.

Ready to explore further? In the next section, you'll practice building pipelines to execute and retrieve results efficiently in C++, enhancing your understanding of Redis pipelines in real-world applications.