Redis

Configure, operate, and optimize Redis for caching, queues, rate limiting, and real-time data storage.

When to Use

• You need a low-latency in-memory cache to reduce database load.
• Your application requires rate limiting, session storage, or leaderboards.
• You need pub/sub messaging between services.
• You want a distributed lock or job queue backed by an in-memory store.

Prerequisites

• Linux server or Docker.
• Root or sudo access for package installation.
• Redis 7.x recommended for production.

Installation and Setup

# Debian / Ubuntu
sudo apt update
sudo apt install -y redis-server

# RHEL / Amazon Linux
sudo dnf install -y redis

# Start and enable
sudo systemctl enable --now redis-server

# Verify
redis-cli ping
# Expected output: PONG

Core Configuration

Edit /etc/redis/redis.conf:

# Network
bind 0.0.0.0
port 6379
protected-mode yes
requirepass strong_redis_password

# Memory
maxmemory 2gb
maxmemory-policy allkeys-lru

# Connections
maxclients 10000
timeout 300
tcp-keepalive 60

# Logging
loglevel notice
logfile /var/log/redis/redis-server.log

# Security — disable dangerous commands in production
rename-command FLUSHALL ""
rename-command FLUSHDB ""
rename-command CONFIG ""
rename-command DEBUG ""

sudo systemctl restart redis-server

redis-cli Commands Reference

# Connect with authentication
redis-cli -a strong_redis_password

# Connect to a remote host
redis-cli -h 10.0.0.5 -p 6379 -a strong_redis_password

String Operations

SET user:1:name "Alice"
GET user:1:name

# Set with TTL (seconds)
SETEX session:abc123 3600 '{"userId":1}'

# Set only if key does not exist (distributed lock pattern)
SET lock:order:42 "worker-1" NX EX 30

# Increment counters
INCR page:views:/home
INCRBY api:quota:user:1 -1

Hash Operations

HSET user:1 name "Alice" email "alice@example.com" plan "pro"
HGET user:1 email
HGETALL user:1
HINCRBY user:1 login_count 1

List Operations (Queues)

LPUSH queue:emails '{"to":"alice@example.com","subject":"Welcome"}'
RPOP queue:emails
LLEN queue:emails

# Blocking pop (worker pattern)
BRPOP queue:emails 30

Set and Sorted Set Operations

# Sets — unique tags
SADD article:1:tags "redis" "database" "caching"
SMEMBERS article:1:tags
SISMEMBER article:1:tags "redis"

# Sorted sets — leaderboards
ZADD leaderboard 1500 "player:1" 2300 "player:2" 1800 "player:3"
ZREVRANGE leaderboard 0 9 WITHSCORES
ZINCRBY leaderboard 100 "player:1"
ZRANK leaderboard "player:2"

Key Management

KEYS user:*             # avoid in production — use SCAN instead
SCAN 0 MATCH user:* COUNT 100
TTL session:abc123
PERSIST session:abc123
DEL user:old
EXPIRE user:1 86400
TYPE user:1

Persistence

RDB Snapshots

# redis.conf — save snapshots at intervals
save 900 1       # snapshot if >= 1 key changed in 900 seconds
save 300 10      # snapshot if >= 10 keys changed in 300 seconds
save 60 10000    # snapshot if >= 10000 keys changed in 60 seconds

dbfilename dump.rdb
dir /var/lib/redis
rdbcompression yes

AOF (Append-Only File)

appendonly yes
appendfilename "appendonly.aof"
appendfsync everysec    # good balance of safety and performance
# Options: always (safest, slowest), everysec (recommended), no (OS decides)

# AOF rewrite thresholds
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb

Recommended Production Strategy

Use both RDB and AOF together. RDB provides fast restarts and compact backups. AOF provides durability down to 1-second granularity.

save 900 1
save 300 10
appendonly yes
appendfsync everysec

Redis Sentinel (High Availability)

Sentinel monitors Redis instances and performs automatic failover.

Sentinel Configuration

# /etc/redis/sentinel.conf
port 26379
sentinel monitor mymaster 10.0.0.1 6379 2
sentinel auth-pass mymaster strong_redis_password
sentinel down-after-milliseconds mymaster 5000
sentinel failover-timeout mymaster 60000
sentinel parallel-syncs mymaster 1

Run at least three Sentinel instances for quorum.

# Start Sentinel
redis-sentinel /etc/redis/sentinel.conf

# Query Sentinel
redis-cli -p 26379 SENTINEL masters
redis-cli -p 26379 SENTINEL get-master-addr-by-name mymaster
redis-cli -p 26379 SENTINEL replicas mymaster

Redis Cluster Mode

Cluster mode distributes data across multiple shards automatically.

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