Redis : Simple Guide

2 minute read

What is Redis?

Redis (Remote Dictionary Server) is an in-memory, key-value data store known for speed, simplicity, and scalability. It stores data in RAM, making read and write operations extremely fast compared to traditional databases. https://redis.io/

  • Performance: Sub-millisecond response times
  • Data Structures: Supports Strings, Lists, Sets, Hashes, Sorted Sets, Bitmaps, etc.
  • Persistence: Can optionally save data to disk for durability
  • Scalability: Supports replication, clustering, and partitioning
  • Pub/Sub & Streaming: Supports real-time messaging

Common Use Cases of Redis

Redis is widely used for caching frequently accessed data, reducing database load and improving performance.
Example:

  • Storing user sessions in a web app
  • Caching API responses
  • Caching database query results

Example in Python (FastAPI Cache with Redis)

import redis

cache = redis.Redis(host="localhost", port=6379, decode_responses=True)

# Set cache
cache.setex("user:123", 3600, "John Doe")  # Expiry in 1 hour

# Get cache
print(cache.get("user:123"))  # Output: John Doe

2. Session Management & Authentication

Since Redis is super fast, it’s great for storing user sessions instead of using cookies or database sessions.
Example:

  • Storing JWT session tokens
  • Keeping track of logged-in users

Example: Storing session data

cache.set("session:abc123", "user_id_456", ex=3600)  # Expires in 1 hour

3. Real-time Analytics & Leaderboards

Redis Sorted Sets (ZSET) help in ranking systems, making it ideal for leaderboards, analytics, and scoring systems.
Example:

  • Gaming leaderboards
  • Real-time analytics
  • Top trending topics

Example: Leaderboard in Redis

cache.zadd("game_leaderboard", {"player1": 100, "player2": 200})
print(cache.zrevrange("game_leaderboard", 0, -1, withscores=True))  # Highest first

4. Pub/Sub (Real-time Messaging & Notifications)

Redis Pub/Sub allows applications to send real-time messages between users or services.
Example:

  • Chat applications
  • Notifications & alerts
  • Real-time streaming data

Example:
Publisher:

cache.publish("notifications", "New user signed up!")

Subscriber:

pubsub = cache.pubsub()
pubsub.subscribe("notifications")

for message in pubsub.listen():
    print(message)  # Listen for new messages

5. Rate Limiting (API Throttling)

Redis is great for limiting API requests (e.g., only 10 requests per minute per user).
Example:

  • Prevent brute force login attacks
  • Throttle API usage
  • Limit form submissions

Example:

user_ip = "192.168.1.1"
key = f"rate_limit:{user_ip}"
if cache.incr(key) == 1:
    cache.expire(key, 60)  # Allow 10 requests per minute

if int(cache.get(key)) > 10:
    print("Rate limit exceeded!")

6. Job Queues & Background Processing

Redis Lists and Streams can be used as task queues for background processing.
Example:

  • Celery task queues
  • Asynchronous job processing

Example: Adding tasks to a queue

cache.lpush("task_queue", "send_email")

Worker processing tasks

while True:
    task = cache.rpop("task_queue")
    if task:
        print(f"Processing {task}")

Summary: Why Use Redis?

Feature Benefit
Super Fast In-memory storage with sub-millisecond latency
Flexible Data Types Supports strings, lists, sets, hashes, sorted sets
Persistence Can save snapshots to disk for durability
Replication Master-slave replication for high availability
Pub/Sub Real-time messaging for chat and notifications
Scalable Supports clustering and partitioning

When to Use Redis?

Yes, use Redis when:

  • You need ultra-fast reads/writes
  • Caching frequently accessed data
  • Storing real-time leaderboard or analytics
  • Managing user sessions
  • Implementing rate limiting

Avoid Redis when:

  • You need strong durability (e.g., financial transactions)
  • Your dataset is too large for RAM
  • Complex relational queries are required

Redis Installation on Ubuntu 22 OS

To install via Snap, run:

sudo apt update
sudo apt install redis-tools # for redis-cli
sudo snap install redis

sudo systemctl status snap.redis.server.service  # check status

# start , stop or reestart
sudo systemctl start snap.redis.server.service
sudo systemctl stop snap.redis.server.service
sudo systemctl restart snap.redis.server.service

# OR using snap
sudo snap start redis
sudo snap stop redis
sudo snap restart redis

# To get ping pong
redis-cli ping

# check the port
redis-cli info | grep port

# check chache params
CONFIG GET *

# chache stats
INFO MEMORY

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