tech

Redis

In-memory data store for caching, sessions, and real-time analytics - blazing fast key-value operations

TL;DR

What: In-memory data structure store - cache, database, message broker.

Why: Ultra-fast reads/writes, simple API, versatile data structures.

Quick Start

Install:

# macOS
brew install redis
brew services start redis

# Ubuntu/Debian
sudo apt install redis-server
sudo systemctl start redis

# Docker
docker run -d --name redis -p 6379:6379 redis:7

Connect:

redis-cli

# Remote
redis-cli -h hostname -p 6379 -a password

Basic operations:

# String
SET name "Alice"
GET name

# With expiration (seconds)
SET session "abc123" EX 3600

# Check TTL
TTL session

# Delete
DEL name

Cheatsheet

Command	Description
`SET key value`	Set string value
`GET key`	Get string value
`DEL key`	Delete key
`EXISTS key`	Check if key exists
`EXPIRE key seconds`	Set expiration
`TTL key`	Get remaining TTL
`KEYS pattern`	Find keys (use SCAN in prod)
`FLUSHDB`	Delete all keys in DB
`INFO`	Server information

Data structures:

# List
LPUSH mylist "a" "b" "c"
LRANGE mylist 0 -1

# Set
SADD myset "a" "b" "c"
SMEMBERS myset

# Hash
HSET user:1 name "Alice" age 30
HGETALL user:1

# Sorted Set
ZADD leaderboard 100 "player1" 200 "player2"
ZRANGE leaderboard 0 -1 WITHSCORES

Gotchas

Connection refused

# Check if Redis is running
redis-cli ping  # Should return PONG

# Check service status
sudo systemctl status redis

# Check if binding to localhost only
# In redis.conf: bind 127.0.0.1

NOAUTH Authentication required

# Connect with password
redis-cli -a yourpassword

# Or after connecting
AUTH yourpassword

# Set password in redis.conf
requirepass yourpassword

Memory issues

# Check memory usage
redis-cli INFO memory

# Set max memory
# redis.conf: maxmemory 256mb
# redis.conf: maxmemory-policy allkeys-lru

Don’t use KEYS in production

# KEYS blocks the server - use SCAN instead
SCAN 0 MATCH "user:*" COUNT 100