# Postgres to Redis Rate Limiting Migration Reference

## Overview
This document provides guidance for migrating API rate limiting from Postgres to Redis in the Fiddy Finance Buddy App. It covers:
- Rate limiting tiers and keying strategies
- Migration triggers and operational considerations
- Redis setup, scaling, monitoring, and best practices
- Example config (not enabled by default)

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## Rate Limiting Tiers & Keying
- **Auth endpoints (login/register):** Strict limits per IP and identifier (email)
- **Write endpoints (POST/PUT/DELETE):** Moderate limits per user and IP
- **Read endpoints (GET):** Higher limits per user and IP
- **Keying:**
  - Unauthenticated: IP only
  - Auth endpoints: IP + email
  - Authenticated: user ID + IP

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## Migration Triggers
Switch to Redis if:
- API request volume or burst traffic causes DB contention or latency
- Postgres rate limit table grows rapidly or cleanup becomes burdensome
- You need native TTL, atomic counters, or horizontal scaling

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## Redis Management & Planning
### Setup
- Provision Redis (self-hosted or managed)
- Secure networking, secrets, and access control
- Integrate Redis client in backend (e.g., `ioredis` or `redis` npm package)

### Scaling
- Monitor memory usage, eviction policy, and connection pools
- Use Redis clustering/replication for high availability

### Monitoring
- Set up alerting for latency, memory, and connection errors
- Track rate limit key usage and eviction

### TTL & Data Retention
- Use Redis native TTL for expiring rate limit keys
- No manual cleanup required

### Backup
- Backups are optional for rate limit counters
- Focus on monitoring and HA

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## Example Redis Config (Not Enabled by Default)

### docker-compose.yml (add, but comment out)
```
# redis:
#   image: redis:7
#   ports:
#     - "6379:6379"
#   restart: unless-stopped
```

### .env.example
```
# REDIS_URL=redis://localhost:6379
```

### Node.js Integration Example
```
// ...existing code...
// import Redis from 'ioredis';
// const redis = new Redis(process.env.REDIS_URL);
// ...existing code...
```

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## Best Practices
- Document migration triggers in backend guidance
- Keep Redis config ready but disabled until needed
- Reference this doc in PROJECT_INSTRUCTIONS.md for future backend work

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## References
- [Redis Official Docs](https://redis.io/docs/)
- [ioredis npm package](https://www.npmjs.com/package/ioredis)
- [Rate limiting patterns](https://redis.io/docs/management/rate-limiting/)

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_Last updated: 2026-02-09_