typescript
async function getUser(userId: string): Promise<User> {
  // 1. Check cache first
  const cached = await redis.get(`user:${userId}`);
  if (cached) return JSON.parse(cached);
  
  // 2. Cache miss — query database
  const user = await db.users.findById(userId);
  
  // 3. Store in cache with TTL
  await redis.setex(`user:${userId}`, 3600, JSON.stringify(user));
  
  return user;
}

typescript
async function updateUser(userId: string, data: Partial<User>) {
  // Update database AND cache together
  const user = await db.users.update(userId, data);
  await redis.setex(`user:${userId}`, 3600, JSON.stringify(user));
  return user;
}

typescript
// Store session in Redis (replaces file/memory sessions)
app.use(session({
  store: new RedisStore({ client: redis }),
  secret: process.env.SESSION_SECRET,
  resave: false,
  saveUninitialized: false,
  cookie: { 
    maxAge: 86400000, // 24 hours
    httpOnly: true,
    secure: true
  }
}));

typescript
async function rateLimit(ip: string, limit: number, window: number): Promise<boolean> {
  const key = `rate:${ip}`;
  const current = await redis.incr(key);
  
  if (current === 1) {
    await redis.expire(key, window);
  }
  
  return current <= limit;
}

// Usage: 100 requests per 60 seconds
if (!(await rateLimit(req.ip, 100, 60))) {
  return res.status(429).json({ error: 'Too many requests' });
}

typescript
import { Queue, Worker } from 'bullmq';

// Producer
const emailQueue = new Queue('emails', { connection: redis });
await emailQueue.add('welcome', {
  to: 'user@example.com',
  subject: 'Welcome!',
  template: 'welcome'
});

// Consumer
const worker = new Worker('emails', async (job) => {
  await sendEmail(job.data);
  console.log(`Sent ${job.data.subject} to ${job.data.to}`);
}, { connection: redis });

typescript
// Publisher
await redis.publish('notifications', JSON.stringify({
  userId: '123',
  message: 'New order received!',
  type: 'order'
}));

// Subscriber
const subscriber = redis.duplicate();
await subscriber.subscribe('notifications');
subscriber.on('message', (channel, message) => {
  const data = JSON.parse(message);
  // Push to WebSocket client
  wsClients.get(data.userId)?.send(message);
});

typescript
// Add scores
await redis.zadd('leaderboard', 2500, 'player:alice');
await redis.zadd('leaderboard', 3200, 'player:bob');
await redis.zadd('leaderboard', 1800, 'player:charlie');

// Get top 10
const top10 = await redis.zrevrange('leaderboard', 0, 9, 'WITHSCORES');
// ["player:bob", "3200", "player:alice", "2500", ...]

// Get player's rank
const rank = await redis.zrevrank('leaderboard', 'player:alice');
// 1 (0-indexed, so 2nd place)