Welcome back! In the previous lesson, we explored Redis Pipelines, which optimize command execution by batching multiple commands. Today, we’ll focus on Redis Transactions, a powerful feature that queues a group of commands for execution in a single, sequential operation.

By the end of this lesson, you’ll understand how to implement transactions in Redis using Java and Jedis.

Redis Transactions allow you to queue multiple commands and then execute them sequentially once you commit (using EXEC). This is often described as an atomic operation, but it’s important to note:

• Atomic Execution: Commands within a transaction are sent to Redis as a block.
• (Partial) All or Nothing: If a command fails at queue time (e.g., invalid command), the entire transaction is discarded. However, if a command fails at runtime (e.g., type error), Redis will still execute the other commands.
• Isolation: Transactions prevent other clients from executing commands on the keys being modified until the transaction completes.
• Queuing of Commands: Commands are queued after a transaction is initiated with MULTI and only execute on EXEC.

In short, Redis discards the entire transaction if a command cannot be queued correctly, but does not roll back commands if a runtime error occurs after the transaction is committed.