**All commands** within the transaction are executed **simultaneously**. If one of the commands **fails**, none of them will be executed. This ensures **data consistency** by preventing **partial** or **invalid changes**, even if **errors** occur.

# How Transactions Are Used
Transactions are commonly applied when **multiple operations** on data must be performed **together**, such as **incrementing a counter** and **writing related data** to another key. Using transactions ensures that either **all operations** are completed, or **none** are, maintaining **data integrity**.

# Core Commands for Transactions

To **start** a transaction in Redis, use the `MULTI` command. This informs Redis that **all subsequent commands** should be part of the **transaction**.

Once you issue `MULTI`, Redis **queues** the **commands** you want to include in the **transaction**.

```
MULTI
SET key1 "value1"
SET key2 "value2"
```

In this example, the commands `SET key1 "value1"` and `SET key2 "value2"` are not executed **immediately**. Instead, they are added to the **transaction queue** and executed **together** when the `EXEC` **command** is called.

## Executing a Transaction
To **execute** all the **commands** in the **transaction**, use the `EXEC` command. This runs every **queued command** in the **transaction**.

```
EXEC
```

**After calling** `EXEC`, both `SET` operations will be **performed**.

## Cancelling a Transaction
If you decide to **cancel** a **transaction** before **execution**, use the `DISCARD` command. This **clears** all the **commands** in the **transaction queue**, ensuring they will not be **executed**.

After calling `DISCARD`, all the **commands** added to the **transaction** since `MULTI` will be **discarded** and not **executed**.

# Monitoring Keys During a Transaction
During a **transaction**, commands are **queued** but not **executed immediately**. The `WATCH` command can be used to **monitor** specific **keys**. If any of these **keys** are **modified** before the **transaction** is **executed**, the **transaction** will be **aborted** to prevent **data conflicts**.

```
WATCH key1
MULTI
SET key1 "new_value"
EXEC
```

In this example, if the **value** of `key1` **changes** before the `EXEC` command is called, the **transaction** will not be **executed**. This ensures **data consistency**, especially when **multiple clients** attempt to **modify** the same **key** simultaneously.

What happens if one of the commands in a Redis transaction fails?

Which command should be used to start a Redis transaction?

This course will introduce you to the fundamentals of Redis and its use in real-world applications. We'll cover key Redis commands, data types, key expiration and transactions, as well as how to integrate Redis with Spring for efficient data caching.

This section provides an introduction to Redis, highlighting its core features and common use cases. You’ll learn how to install Redis on different platforms, including Windows and macOS, and get familiar with the basics of connecting to and starting the Redis server.

Here, we explore the essential Redis commands for managing and manipulating data effectively. You'll learn how to set, retrieve, increment, and delete data using commands like SET, GET, EXISTS, INCR, DECR, and tackle practical tasks to apply these concepts in real-world scenarios.

Here, you will learn about key Redis data types, including Lists, Sets, Sorted Sets, and Hashes. You will explore their functionality and practical applications through focused exercises designed to reinforce your understanding of each data type.

You'll explore advanced features of Redis, including managing key lifecycles, executing transactions, and leveraging the Pub/Sub messaging system. Additionally, you'll learn essential security practices to safeguard your Redis environment against unauthorized access.

This section introduces the fundamentals of caching and demonstrates how to configure Redis as a cache in a Spring application. It covers key caching annotations and practical examples of caching queries in web applications, concluding with a summary of the main concepts.

Introduction to Redis

Transactions

How Transactions Are Used

Core Commands for Transactions

Executing a Transaction

Cancelling a Transaction

Monitoring Keys During a Transaction

1. What happens if one of the commands in a Redis transaction fails?

2. Which command should be used to start a Redis transaction?