Redis

Redis (Remote Dictionary Server) is an open-source, in-memory, key-value data store primarily used as a cache, message broker, and database. It supports high-performance read/write operations, making it one of the fastest databases available.

Key Features:

• In-Memory Storage: Stores data in RAM for ultra-fast access.
• Key-Value Data Model: Supports strings, lists, sets, hashes, bitmaps, and more.
• Persistence Options: Can save data to disk with snapshots or append-only files (AOF).
• Pub/Sub Messaging: Enables real-time communication between processes.
• Replication & Clustering: Supports master-slave replication for high availability.
• Atomic Transactions: Uses Lua scripting for multi-step commands.

Why Use Redis?

• Super Fast: Redis operates in memory, making it significantly faster than traditional databases.
• Versatile Data Structures: Unlike simple key-value stores, Redis supports lists, sets, and more.
• Caching: Redis is commonly used for caching database queries, session data, and API responses.
• Real-Time Processing: Used in chat applications, gaming leaderboards, and analytics.
• Scalability: Supports replication and clustering for distributed deployments.

Redis Data Types & Commands

Data Type	Description	Example Command
**St Simple key-value pairs ] ] ] ] ] ]	SET name "Alice"
List	Ordered co	LPUSH mylist 10 20 30
Set		SADD myset "apple" "banana"
Hash	[[	HSET user:1 name "Alice" age 25
Sorted Set	a r ing ore	ZADD leaderboard 100 "player1"

Using Redis as a Cache

Redis is commonly used for caching database queries, API responses, and session data.

Example: Caching with Expiry Time

SET user:1001 "John Doe" EX 3600  # Expires in 1 hour

This reduces database load and improves response times.

Redis Pub/Sub (Message Queue)

Redis can handle real-time messaging with publish-subscribe (Pub/Sub).

Example: Publishing and Subscribing to a Channel

SUBSCRIBE news_channel
PUBLISH news_channel "Breaking News: Redis is awesome!"

Useful for chat apps, notifications, and event-driven systems.

Redis Persistence (Data Backup & Recovery)

Redis offers two persistence methods:

1. RDB (Redis Database File): Creates snapshots of data at set intervals.
2. AOF (Append-Only File): Logs each write operation for durability.

Enable Persistence in redis.conf:

save 900 1   # Save every 900 seconds if at least 1 change occurs
appendonly yes  # Enable AOF for durability

This prevents data loss in case of system failures.

Scaling Redis (Replication & Clustering)

Master-Slave Replication

Redis supports one master with multiple read-only slaves to distribute read requests.

SLAVEOF 192.168.1.10 6379  # Make a Redis instance a replica of another

Redis Clustering

Redis Cluster partitions data across multiple nodes, enabling horizontal scaling.

redis-cli --cluster create 192.168.1.1:6379 192.168.1.2:6379 192.168.1.3:6379 --cluster-replicas 1

Example: Integrating Redis with Python

1. Installing Redis Client for Python

pip install redis

2. Usage in python

import redis
 
# Connect to Redis
r = redis.Redis(host='localhost', port=6379, decode_responses=True)
 
# Set and Get a value
r.set("user:1", "Alice")
print(r.get("user:1"))  # Output: Alice