BE_4 - Redis and WebSocket Setup

[notjackl3]

Summary

Set up Redis connections for caching, pub/sub, and rate limiting with utility functions for common operations.
[Estimated hours: 9-10]

Objectives

• Configure three separate Redis client instances
• Create utility functions for caching
• Create utility functions for rate limiting
• Add health check endpoint
• Document Redis data structures in README

Description

Redis serves multiple purposes in AskEasy:

1. Caching - Session data, stats (reduce DB load)
2. Pub/Sub - Socket.IO message broker for horizontal scaling
3. Rate Limiting - Prevent spam/abuse

Each purpose uses a separate Redis database (0, 1, 2) for isolation.

Technical Details

File Structure

src/lib/
├── redis.ts           # Client instances
├── cache.ts           # Caching utilities
├── rateLimit.ts       # Rate limiting utilities
└── redisKeys.ts       # Key naming conventions

Redis Clients

// Database 0: General caching
export const redisCache = new Redis(process.env.REDIS_URL, { db: 0 });

// Database 1: Pub/Sub (Socket.IO)
export const redisPubSub = new Redis(process.env.REDIS_URL, { db: 1 });

// Database 2: Rate limiting
export const redisRateLimit = new Redis(process.env.REDIS_URL, { db: 2 });

Key Utility Functions

1. cacheSession(sessionId, data, ttl) - Cache active session
2. getSessionCache(sessionId) - Retrieve cached session
3. invalidateSessionCache(sessionId) - Clear cache
4. checkRateLimit(key, limit, window) - Rate limit check
5. incrementRateLimit(key, window) - Increment counter

Acceptance Criteria

• Three Redis clients connect successfully on startup
• Can set and get values from cache with TTL
• Rate limit function correctly blocks after limit exceeded
• Health check endpoint returns Redis connection status
• Error handling for Redis connection failures (logs error, doesn't crash)
• Documentation in README explains Redis structure
• Can view Redis data using redis-cli or Redis Commander

Resources

• ioredis Documentation
• Redis Rate Limiting Pattern
• Redis Best Practices