Redis

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 "[email protected]" plan "pro"
HGET user:1 email
HGETALL user:1
HINCRBY user:1 login_count 1

List Operations (Queues)

LPUSH queue:emails '{"to":"[email protected]","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.

# Create a 6-node cluster (3 masters + 3 replicas)
redis-cli --cluster create \
  10.0.0.1:6379 10.0.0.2:6379 10.0.0.3:6379 \
  10.0.0.4:6379 10.0.0.5:6379 10.0.0.6:6379 \
  --cluster-replicas 1 -a strong_redis_password

# Check cluster status
redis-cli -c -a strong_redis_password CLUSTER INFO
redis-cli -c -a strong_redis_password CLUSTER NODES

# Add a new node
redis-cli --cluster add-node 10.0.0.7:6379 10.0.0.1:6379

# Rebalance slots
redis-cli --cluster rebalance 10.0.0.1:6379

# redis.conf for cluster nodes
cluster-enabled yes
cluster-config-file nodes.conf
cluster-node-timeout 5000

Common Patterns

Caching with TTL

# Cache a database query result for 5 minutes
SET cache:user:42:profile '{"name":"Alice","plan":"pro"}' EX 300

# Cache-aside pattern (pseudocode):
# 1. GET cache:key -> if hit, return
# 2. Query database
# 3. SET cache:key result EX 300
# 4. Return result

Rate Limiting (Sliding Window)

# Allow 100 requests per minute per user
# Using a sorted set with timestamps as scores
ZADD ratelimit:user:42 1700000000.123 "req-uuid-1"
ZREMRANGEBYSCORE ratelimit:user:42 0 1699999940.000
ZCARD ratelimit:user:42
EXPIRE ratelimit:user:42 60
# If ZCARD >= 100, reject the request

Pub/Sub Messaging

# Terminal 1 — subscriber
redis-cli -a strong_redis_password
SUBSCRIBE notifications:order-updates

# Terminal 2 — publisher
redis-cli -a strong_redis_password
PUBLISH notifications:order-updates '{"orderId":42,"status":"shipped"}'

# Pattern subscription
PSUBSCRIBE notifications:*

Distributed Locking (Redlock Pattern)

# Acquire lock
SET lock:resource:42 "worker-abc" NX EX 30
# Returns OK if acquired, nil if already held

# Release lock (use Lua script to ensure atomicity)
redis-cli -a strong_redis_password EVAL "
  if redis.call('get', KEYS[1]) == ARGV[1] then
    return redis.call('del', KEYS[1])
  else
    return 0
  end
" 1 lock:resource:42 "worker-abc"

Docker Compose Setup

# docker-compose.yml