Back to Redis Course
Module 1
📘 Redis Fundamentals
Understand what Redis is, when to use it, and get hands-on with the basics.
What is Redis?
Redis (Remote Dictionary Server) is an open-source, in-memory data structure store that can be used as a database, cache, message broker, and streaming engine.
In-Memory Data Store vs Traditional DB
| Aspect | Redis (In-Memory) | Traditional DB (Disk-Based) |
|---|---|---|
| Speed | Sub-millisecond latency | Milliseconds to seconds |
| Storage | RAM (limited by memory) | Disk (virtually unlimited) |
| Persistence | Optional (RDB/AOF) | Built-in & durable |
| Data Model | Key-Value + Rich Data Types | Tables, Documents, etc. |
Redis Use Cases
🚀 Caching
Store frequently accessed data to reduce DB load and improve response times.
📋 Message Queue
Use Lists or Streams for async task processing and job queues.
🔐 Session Store
Distributed session management for web applications.
🏆 Leaderboards
Real-time rankings using Sorted Sets with O(log N) operations.
Redis Architecture
Single-Threaded Model (Myth vs Reality)
⚠️ Common Misconception
"Redis is single-threaded, so it can't be fast" — WRONG!
The Reality:
- Redis uses a single thread for command execution (atomic operations)
- Since Redis 6.0, I/O is handled by multiple threads
- Background threads handle persistence (RDB snapshots, AOF rewriting)
- No locks needed = No lock contention = Extremely fast
Event Loop & I/O Multiplexing
Redis Architecture Diagram
┌─────────────────────────────────────────────────┐
│ Redis Server │
├─────────────────────────────────────────────────┤
│ │
│ ┌─────────────┐ ┌──────────────────────┐ │
│ │ Clients │───▶│ I/O Multiplexer │ │
│ │ (1000s) │ │ (epoll/kqueue) │ │
│ └─────────────┘ └──────────┬───────────┘ │
│ │ │
│ ┌────────────▼────────────┐ │
│ │ Single-Threaded │ │
│ │ Command Processor │ │
│ │ (Main Event Loop) │ │
│ └────────────┬────────────┘ │
│ │ │
│ ┌────────────▼────────────┐ │
│ │ In-Memory Data Store │ │
│ └─────────────────────────┘ │
│ │
└─────────────────────────────────────────────────┘Redis Installation & Setup
Option 1: Docker-Based Redis (Recommended)
Docker Commands
# Pull and run Redis containerdocker run -d--name redis-server -p6379:6379 redis:latest
# With persistencedocker run -d--name redis-server \-p6379:6379 \-v redis-data:/data \
redis:latest redis-server --appendonlyyes# Connect to Redis CLIdockerexec-it redis-server redis-cliOption 2: Local Installation
🐧 Linux/WSL
Linux
sudoapt update
sudoaptinstall redis-server
sudo systemctl start redis🍎 macOS
macOS
brew install redis
brew services start redisVerify Installation
Verification
$ redis-cli ping
PONG
$ redis-cli info server |head-5# Server
redis_version:7.0.11
redis_git_sha1:00000000
redis_git_dirty:0Redis CLI Basics
Essential Commands
Redis CLI - Basic Commands
# SET & GET - Basic key-value operations127.0.0.1:6379> SET user:1:name "John Doe"
OK
127.0.0.1:6379> GET user:1:name
"John Doe"# EXISTS - Check if key exists127.0.0.1:6379> EXISTS user:1:name
(integer)1127.0.0.1:6379> EXISTS user:999:name
(integer)0# DEL - Delete keys127.0.0.1:6379> DEL user:1:name
(integer)1# KEYS - Find keys by pattern (⚠️ Avoid in production!)127.0.0.1:6379> KEYS user:*
1)"user:1:email"2)"user:2:name"TTL & EXPIRE - Key Expiration
Redis CLI - TTL Commands
# SET with expiration (EX = seconds, PX = milliseconds)127.0.0.1:6379> SET session:abc123 "user-data" EX 3600
OK
# Set expiration on existing key127.0.0.1:6379> EXPIRE cache:products 300(integer)1# Check remaining TTL127.0.0.1:6379> TTL session:abc123
(integer)3595# Remove expiration (make key persistent)127.0.0.1:6379> PERSIST session:abc123
(integer)1# SETEX shorthand (SET + EXPIRE in one command)127.0.0.1:6379> SETEX cache:homepage 60"<html>...</html>"
OK💡 Pro Tip
Use NX (only if Not eXists) and XX (only if eXists) for conditional sets:SET lock:order123 "locked" NX EX 30 — Sets only if key doesn't exist (distributed lock!)