Advanced Node.js

Chapter 10: Caching Strategies

10.1 Redis Caching

Redis is an in-memory data store used for caching, session storage, and real-time analytics.

const redis = require('redis');
const client = redis.createClient();

await client.connect();

// Set cache
await client.set('user:1', JSON.stringify(userData), {
    EX: 3600 // Expire after 1 hour
});

// Get cache
const cached = await client.get('user:1');
if (cached) {
    return JSON.parse(cached);
}

// Cache with fallback
async function getCachedUser(userId) {
    const cacheKey = `user:${userId}`;
    const cached = await client.get(cacheKey);
    
    if (cached) {
        return JSON.parse(cached);
    }
    
    const user = await db.getUser(userId);
    await client.setEx(cacheKey, 3600, JSON.stringify(user));
    return user;
}

10.2 Cache Patterns

Cache-Aside (Lazy Loading):

// Application checks cache first
async function getData(key) {
    let data = await cache.get(key);
    if (!data) {
        data = await database.get(key);
        await cache.set(key, data);
    }
    return data;
}

Write-Through:

// Write to cache and database simultaneously
async function updateData(key, value) {
    await database.set(key, value);
    await cache.set(key, value);
}

10.3 Cache Invalidation

// Invalidate on update
async function updateUser(userId, data) {
    await db.updateUser(userId, data);
    await cache.del(`user:${userId}`);
    // Or update cache
    await cache.set(`user:${userId}`, data);
}