Redis Skill

Redis session store, caching, and Bull job queues for Node.js/Express backends. This codebase currently uses in-memory solutions that should be replaced with Redis for production scalability and multi-instance deployments.

WARNING: Missing Redis Implementation

Detected: No ioredis, redis, or bullmq in backend dependencies. Impact: Rate limiting and caching fail across multiple server instances.

cd backend
npm install ioredis bullmq
npm install -D @types/ioredis

Quick Start

Redis Client Setup

// src/config/redis.ts
import Redis from 'ioredis';

const redis = new Redis({
  host: process.env.REDIS_HOST || 'localhost',
  port: parseInt(process.env.REDIS_PORT || '6379'),
  password: process.env.REDIS_PASSWORD,
  maxRetriesPerRequest: 3,
  retryDelayOnFailover: 100,
  enableReadyCheck: true,
});

redis.on('error', (err) => console.error('Redis error:', err));
redis.on('connect', () => console.log('Redis connected'));

export { redis };

Replace In-Memory Rate Limiter

// src/middleware/redisRateLimiter.ts
import { redis } from '../config/redis';
import { Request, Response, NextFunction } from 'express';

export async function redisRateLimiter(
  key: string,
  maxRequests: number,
  windowMs: number
) {
  return async (req: Request, res: Response, next: NextFunction) => {
    const identifier = `ratelimit:${key}:${req.ip}`;
    const current = await redis.incr(identifier);
    
    if (current === 1) {
      await redis.pexpire(identifier, windowMs);
    }
    
    if (current > maxRequests) {
      const ttl = await redis.pttl(identifier);
      res.setHeader('Retry-After', Math.ceil(ttl / 1000));
      return res.status(429).json({ message: 'Too many requests' });
    }
    
    next();
  };
}

Key Concepts

| Concept | Usage | Example | |---------|-------|---------| | Caching | API response caching | redis.setex('products:list', 300, JSON.stringify(data)) | | Rate Limiting | Request throttling | redis.incr() with pexpire() | | Sessions | JWT token blacklist | redis.set('blacklist:token', '1', 'EX', 86400) | | Job Queues | Background tasks | new Queue('emails', { connection: redis }) | | Pub/Sub | Real-time events | redis.publish('order:created', orderId) |

Common Patterns

Cache-Aside Pattern

When: Caching expensive database queries or API responses.

async function getProducts(lang: string): Promise<Product[]> {
  const cacheKey = `products:${lang}`;
  const cached = await redis.get(cacheKey);
  
  if (cached) return JSON.parse(cached);
  
  const products = await productService.getAll(lang);
  await redis.setex(cacheKey, 300, JSON.stringify(products));
  return products;
}

Cache Invalidation

When: Data changes and cached values become stale.

async function updateProduct(id: number, data: ProductUpdate) {
  await productService.update(id, data);
  
  // Invalidate all product-related caches
  const keys = await redis.keys('products:*');
  if (keys.length) await redis.del(...keys);
}

See Also

• patterns - Caching, rate limiting, sessions
• workflows - Setup, Bull queues, monitoring

Related Skills

• See the express skill for middleware integration
• See the postgresql skill for cache invalidation on DB changes
• See the docker skill for Redis container configuration
• See the node skill for async patterns with Redis