Redis
Caching, data structures, and real-time patterns.
CLI Basics
# Connect
redis-cli
redis-cli -h hostname -p 6379 -a password
# Ping
redis-cli ping # PONG
# Info
redis-cli info
redis-cli info memory
redis-cli info keyspace
Strings
# Set/get
SET key "value"
GET key
# With expiration
SET session:abc "user123" EX 3600 # 1 hour
SETEX session:abc 3600 "user123" # Same thing
# Set if not exists
SETNX lock:resource "owner123"
# Increment/decrement
INCR counter
INCRBY counter 5
DECR counter
# Multiple
MSET key1 "val1" key2 "val2"
MGET key1 key2
Hashes
# Set fields
HSET user:1 name "Alice" email "alice@test.com" age 30
# Get
HGET user:1 name
HGETALL user:1
HMGET user:1 name email
# Increment field
HINCRBY user:1 age 1
# Check existence
HEXISTS user:1 email
# Delete field
HDEL user:1 age
Lists
# Push
LPUSH queue "task1" # Left (head)
RPUSH queue "task2" # Right (tail)
# Pop
LPOP queue # Left
RPOP queue # Right
BLPOP queue 30 # Blocking pop (timeout 30s)
# Range
LRANGE queue 0 -1 # All elements
LRANGE queue 0 9 # First 10
# Length
LLEN queue
# Trim (keep only range)
LTRIM queue 0 99 # Keep first 100
Sets
# Add/remove
SADD tags "python" "redis" "docker"
SREM tags "docker"
# Check membership
SISMEMBER tags "python"
# All members
SMEMBERS tags
# Count
SCARD tags
# Operations
SUNION tags1 tags2 # Union
SINTER tags1 tags2 # Intersection
SDIFF tags1 tags2 # Difference
# Random
SRANDMEMBER tags 2 # 2 random members
Sorted Sets
# Add with score
ZADD leaderboard 100 "alice" 95 "bob" 87 "charlie"
# Get by rank
ZRANGE leaderboard 0 -1 WITHSCORES # Ascending
ZREVRANGE leaderboard 0 2 WITHSCORES # Top 3
# Get by score
ZRANGEBYSCORE leaderboard 90 100 # Score 90-100
# Rank
ZRANK leaderboard "alice" # 0-based position
ZREVRANK leaderboard "alice" # Reverse rank
# Increment score
ZINCRBY leaderboard 5 "bob"
# Count in range
ZCOUNT leaderboard 80 100
Key Management
# Find keys
KEYS user:* # Pattern match (avoid in production)
SCAN 0 MATCH user:* COUNT 100 # Safe iteration
# Expiration
EXPIRE key 3600 # Set TTL (seconds)
PEXPIRE key 3600000 # Milliseconds
TTL key # Check TTL
PERSIST key # Remove expiration
# Delete
DEL key
UNLINK key # Async delete (large keys)
# Type
TYPE key
# Exists
EXISTS key
Pub/Sub
# Subscribe
SUBSCRIBE channel1 channel2
# Pattern subscribe
PSUBSCRIBE news.*
# Publish
PUBLISH channel1 "Hello subscribers!"
# Unsubscribe
UNSUBSCRIBE channel1
Common Patterns
Caching
# Cache-aside pattern
# 1. Check cache
GET cache:user:1
# 2. If miss, query DB, then set cache
SET cache:user:1 '{"name":"Alice"}' EX 300 # 5 min TTL
Rate Limiting
# Sliding window rate limit
# Using sorted set with timestamp scores
ZADD ratelimit:user:1 <timestamp> <request-id>
ZREMRANGEBYSCORE ratelimit:user:1 0 <timestamp-window-ago>
ZCARD ratelimit:user:1
# If count > limit, reject
Session Store
SET session:<session-id> '{"userId":1,"role":"admin"}' EX 86400
GET session:<session-id>
Distributed Lock
# Acquire lock
SET lock:resource <unique-id> NX EX 30
# NX = only if not exists, EX = auto-expire
# Release lock (use Lua for atomicity)
EVAL "if redis.call('GET',KEYS[1]) == ARGV[1] then return redis.call('DEL',KEYS[1]) else return 0 end" 1 lock:resource <unique-id>
Configuration
# Max memory
CONFIG SET maxmemory 256mb
CONFIG SET maxmemory-policy allkeys-lru
# Eviction policies:
# noeviction - Return error on write when full
# allkeys-lru - Evict least recently used
# allkeys-lfu - Evict least frequently used
# volatile-lru - LRU among keys with TTL
# volatile-ttl - Evict shortest TTL first
# Persistence
CONFIG SET save "900 1 300 10" # RDB snapshots
CONFIG SET appendonly yes # AOF log
# View config
CONFIG GET maxmemory*
Reference
For caching patterns, pub/sub, and Lua scripts: references/patterns.md