Redis Expert

Expert guidance for Redis - the in-memory data structure store used as cache, message broker, and database with microsecond latency.

Core Concepts

Data Structures

• Strings (binary-safe, up to 512MB)
• Lists (linked lists)
• Sets (unordered unique strings)
• Sorted Sets (sets ordered by score)
• Hashes (field-value pairs)
• Streams (append-only log)
• Bitmaps and HyperLogLog
• Geospatial indexes

Key Features

• In-memory storage with persistence
• Pub/Sub messaging
• Transactions
• Lua scripting
• Pipelining
• Master-Replica replication
• Redis Sentinel (high availability)
• Redis Cluster (horizontal scaling)

Use Cases

• Caching layer
• Session storage
• Real-time analytics
• Message queues
• Rate limiting
• Leaderboards
• Geospatial queries

Installation and Configuration

Docker Setup

# Development
docker run --name redis -p 6379:6379 -d redis:7-alpine

# Production with persistence
docker run --name redis \
  -p 6379:6379 \
  -v redis-data:/data \
  -d redis:7-alpine \
  redis-server --appendonly yes --requirepass strongpassword

# Redis with config file
docker run --name redis \
  -p 6379:6379 \
  -v ./redis.conf:/usr/local/etc/redis/redis.conf \
  -d redis:7-alpine \
  redis-server /usr/local/etc/redis/redis.conf

Configuration (redis.conf)

# Network
bind 0.0.0.0
port 6379
protected-mode yes

# Security
requirepass strongpassword

# Memory
maxmemory 2gb
maxmemory-policy allkeys-lru

# Persistence
save 900 1      # Save after 900s if 1 key changed
save 300 10     # Save after 300s if 10 keys changed
save 60 10000   # Save after 60s if 10000 keys changed

appendonly yes
appendfilename "appendonly.aof"
appendfsync everysec

# Replication
replica-read-only yes
repl-diskless-sync yes

# Performance
tcp-backlog 511
timeout 0
tcp-keepalive 300

Redis Cluster

Setup

# Create 6 nodes (3 masters, 3 replicas)
for port in {7000..7005}; do
  mkdir -p cluster/${port}
  cat > cluster/${port}/redis.conf <<EOF
port ${port}
cluster-enabled yes
cluster-config-file nodes.conf
cluster-node-timeout 5000
appendonly yes
EOF
  redis-server cluster/${port}/redis.conf &
done

# Create cluster
redis-cli --cluster create \
  127.0.0.1:7000 127.0.0.1:7001 127.0.0.1:7002 \
  127.0.0.1:7003 127.0.0.1:7004 127.0.0.1:7005 \
  --cluster-replicas 1

Cluster Client

import Redis from 'ioredis';

const cluster = new Redis.Cluster([
  { host: '127.0.0.1', port: 7000 },
  { host: '127.0.0.1', port: 7001 },
  { host: '127.0.0.1', port: 7002 },
]);

// Operations work transparently
await cluster.set('key', 'value');
await cluster.get('key');

Performance Optimization

Connection Pooling

const redis = new Redis({
  host: 'localhost',
  port: 6379,
  maxRetriesPerRequest: 3,
  enableReadyCheck: true,
  lazyConnect: true,
});

Avoid KEYS Command

// ❌ Bad: Blocks entire server
const keys = await redis.keys('user:*');

// ✅ Good: Use SCAN for large datasets
async function* scanKeys(pattern: string) {
  let cursor = '0';
  do {
    const [newCursor, keys] = await redis.scan(
      cursor,
      'MATCH',
      pattern,
      'COUNT',
      100
    );
    cursor = newCursor;
    yield* keys;
  } while (cursor !== '0');
}

for await (const key of scanKeys('user:*')) {
  console.log(key);
}

Optimize Data Structures

// Use hashes for objects instead of multiple keys
// ❌ Bad: 3 keys
await redis.set('user:1000:name', 'Alice');
await redis.set('user:1000:email', '[email protected]');
await redis.set('user:1000:age', '30');

// ✅ Good: 1 key
await redis.hset('user:1000', {
  name: 'Alice',
  email: '[email protected]',
  age: '30',
});

Anti-Patterns to Avoid

❌ Using Redis as primary database: Use for caching/sessions ❌ Not setting TTL on cache keys: Causes memory bloat ❌ Using KEYS in production: Use SCAN instead ❌ Large values in keys: Keep values small (<1MB) ❌ No monitoring: Track memory, latency, hit rate ❌ Synchronous blocking operations: Use async operations ❌ Not handling connection failures: Implement retry logic ❌ Storing large collections in single key: Split into multiple keys

Common Use Cases

Session Store (Express)

import session from 'express-session';
import RedisStore from 'connect-redis';

app.use(
  session({
    store: new RedisStore({ client: redis }),
    // Session signing secret - from the environment, never a literal.
    secret: process.env.SESSION_SECRET,
    resave: false,
    saveUninitialized: false,
    cookie: {
      secure: true,
      httpOnly: true,
      maxAge: 1000 * 60 * 60 * 24, // 24 hours
    },
  })
);

Job Queue (BullMQ)

import { Queue, Worker } from 'bullmq';

const queue = new Queue('emails', { connection: redis });

// Add job
await queue.add('send-email', {
  to: '[email protected]',
  subject: 'Welcome',
  body: 'Hello!',
});

// Process jobs
const worker = new Worker(
  'emails',
  async (job) => {
    await sendEmail(job.data);
  },
  { connection: redis }
);

Reference Documentation

Detailed material lives alongside this skill and is read on demand:

• [Best Practices](references/BEST_PRACTICES.md) — Memory Management, Key Naming, Expiration, Persistence, Monitoring
• [Node.js Client (ioredis)](references/NODEJSCLIENT_IOREDIS.md) — Basic Operations, Advanced Patterns, Pub/Sub, Redis Streams, Transactions, Pipelining, Lua Scripts

Resources

• Redis Documentation: https://redis.io/docs/
• ioredis: https://github.com/redis/ioredis
• Redis University: https://university.redis.com/
• BullMQ: https://docs.bullmq.io/