In the previous lesson, we explored the basics of Redis Transactions and how they ensure atomic execution of commands. Now, we’ll enhance our understanding by diving into conditional transactions using the WATCH command. This feature allows us to monitor keys for changes before executing a transaction, ensuring data consistency in concurrent environments.

By the end of this lesson, you’ll be able to implement transactions that handle key conflicts effectively.

Conditional transactions in Redis use the WATCH command to monitor specific keys for changes. If any watched key is modified by another client before the transaction is executed, the transaction will abort. This is especially useful in high-concurrency scenarios where multiple clients may access the same data.

Key features of conditional transactions include:

• Conflict Detection: Monitors keys for changes and aborts the transaction if they are modified.
• Ensured Consistency: Guarantees that updates are based on the latest state of data.
• Retry Mechanism: Allows applications to handle failed transactions gracefully and retry as needed.

Using WATCH, you can implement robust solutions to prevent race conditions and maintain data integrity.

Let’s walk through an example of safely updating a user’s balance using the WATCH command. Our goal is to ensure no other client modifies the balance while our transaction is in progress.