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🚀 Redis Essentials: CLI, Configuration, Persistence, and Usage

Redis is a fast, in-memory key-value store widely used for caching, session storage, pub/sub, and real-time analytics. This guide covers how to use Redis from the CLI, configure it for production, manage persistence, and apply practical usage patterns.

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⚡ 1. Redis CLI Basics

🔹 Connecting to Redis

redis-cli
redis-cli -h 127.0.0.1 -p 6379 -a yourpassword

🔹 Common Commands

SET user:1 "John"
GET user:1

DEL user:1
EXISTS user:1
TTL user:1

KEYS user:*        -- (⚠️ avoid in production)
SCAN 0 MATCH user:* COUNT 100

FLUSHDB           -- flush current DB
FLUSHALL          -- flush all DBs

Use SCAN instead of KEYS in production to avoid blocking.

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⚙️ 2. Configuration for Production

🔹 Config File

Default path: /etc/redis/redis.conf (Debian) or /etc/redis.conf (Alpine/Docker)

Important entries:

bind 127.0.0.1
port 6379
requirepass yourpassword
timeout 300
maxmemory 512mb
maxmemory-policy allkeys-lru
appendonly yes
save 900 1
save 300 10

# Test config
redis-server /etc/redis/redis.conf --test-memory 512

# Restart service (Debian)
sudo systemctl restart redis

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🔐 3. Access Control & Security

🔹 Authentication

Enable in config:

requirepass s3cret

Or at runtime:

AUTH s3cret

Use Redis ACLs (redis >= 6.0) for fine-grained control:

ACL SETUSER readonly on >password ~* +@read
ACL SETUSER writer on >password ~* +@write

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💾 4. Persistence Modes

Redis supports two main persistence strategies:

🔹 AOF (Append-Only File)

• Safer, logs each write operation
• Config:

appendonly yes
appendfsync everysec

🔹 RDB Snapshots

• Periodic full memory snapshots
• Config:

save 900 1
save 300 10

Backups are written to:

• /var/lib/redis/dump.rdb
• /var/lib/redis/appendonly.aof

# Trigger save manually
SAVE         # blocking
BGSAVE       # non-blocking

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🧠 5. Redis Data Structures

Type	Example Key Pattern	Commands	Use Case
Strings	user:1:name	GET, SET, INCR	Counters, simple values
Hashes	user:1	HGET, HSET, HGETALL	Objects (user profile, etc.)
Lists	queue:jobs	LPUSH, RPOP, LRANGE	Queues, logs
Sets	tags:post:1	SADD, SMEMBERS, SINTER	Tags, unique values
Sorted Sets	leaderboard	ZADD, ZRANGE, ZREVRANK	Rankings, scores
Bitmaps	feature:flags	SETBIT, GETBIT, BITCOUNT	Flags, tracking on/off bits
HyperLogLog	users:seen	PFADD, PFCOUNT	Approximate cardinality

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🛰️ 6. Redis Pub/Sub

For event messaging and notifications between services:

# Terminal A
SUBSCRIBE events:signup

# Terminal B
PUBLISH events:signup "new_user_id:123"

Redis Pub/Sub is fast but not durable — not guaranteed to deliver if subscriber is offline.

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🔄 7. Use as a Cache (with TTLs)

# Set with TTL
SET session:abc123 "user data" EX 3600

# Get TTL
TTL session:abc123

# Atomic get+set+expire
SET mykey "value" EX 10 NX

Common eviction policies (set in config):

• allkeys-lru (least recently used)
• volatile-ttl (shortest time to live)
• noeviction (reject writes when full)

Use INFO memory to track memory usage.

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🔍 8. Monitoring Redis

🔹 Stats and Info

INFO          -- All stats
INFO memory   -- Memory-specific
MONITOR       -- Live command feed (verbose)
CLIENT LIST   -- Connected clients

🔹 Logging

• Logs found in /var/log/redis/redis-server.log
• Verbosity set in config: loglevel notice

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🧪 9. Useful Tools

• redis-cli – default CLI tool
• RedisInsight – official GUI dashboard
• redis-benchmark – test performance

redis-benchmark -n 100000 -q -P 10

• RDB Tools – inspect .rdb snapshots
• redis-commander – Node-based GUI for live keys

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🛡️ 10. Reliability Tips

• Always set maxmemory and eviction policy in production
• Use AOF for safer persistence
• Use replication (slaveof, replicaof) for HA
• Combine with Sentinel or Redis Cluster for fault tolerance
• Protect Redis from the internet (bind, password, firewalls)

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📚 Resources

• Redis Official Docs
• Redis CLI Reference
• RedisInsight Dashboard

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✅ Summary

Topic	Tool/Command/Config
Connect	redis-cli -a password
Set/Query Keys	SET, GET, EXPIRE, TTL
Persistence	appendonly yes, BGSAVE
Monitor	INFO, MONITOR, CLIENT LIST
Auth & ACLs	requirepass, ACL SETUSER
Eviction	maxmemory-policy allkeys-lru
Use as Cache	SET key val EX 60 NX

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