metabuilder/docs/RATE_LIMITING_GUIDE.md

Rate Limiting Implementation Guide

Status: ✅ COMPLETE Implemented: 2026-01-21 Location: frontends/nextjs/src/lib/middleware/rate-limit.ts

Overview

MetaBuilder now includes a comprehensive rate limiting system to prevent:

• Brute-force attacks on authentication endpoints
• User enumeration attacks (attempting to guess usernames)
• Denial of Service (DoS) attacks on public endpoints
• Bulk data scraping or unauthorized access

Quick Start

Using Rate Limiting in API Routes

// Example: Apply rate limiting in an API route
import type { NextRequest } from 'next/server'
import { applyRateLimit } from '@/lib/middleware'

export async function POST(request: NextRequest) {
  // Check rate limit for login endpoint
  const limitResponse = applyRateLimit(request, 'login')
  if (limitResponse) {
    return limitResponse // Returns 429 Too Many Requests if limit exceeded
  }

  // ... rest of handler
}

Available Rate Limiters

Limiter	Limit	Window	Purpose	Status
login	5	1 minute	Login attempts per IP	✅ Active
register	3	1 minute	Registration attempts	✅ Active
list	100	1 minute	GET list endpoints	✅ Active
mutation	50	1 minute	POST/PUT/PATCH/DELETE	✅ Active
public	1000	1 hour	Public API endpoints	✅ Active
bootstrap	1	1 hour	System bootstrap	✅ Active

Implementation Details

Where Rate Limiting is Applied

1. Main API Route (/api/v1/[...slug])

   • Login: 5 attempts/minute per IP
   • Register: 3 attempts/minute per IP
   • GET requests: 100 requests/minute per IP
   • Mutations: 50 requests/minute per IP

2. Bootstrap Endpoint (/api/bootstrap)

   • Bootstrap: 1 attempt/hour per IP
   • Prevents repeated system initialization

Rate Limit Response

When a rate limit is exceeded, the endpoint returns:

HTTP/1.1 429 Too Many Requests
Content-Type: application/json
Retry-After: 60

{
  "error": "Too many requests",
  "retryAfter": 60
}

IP Detection Strategy

Rate limiting uses the client's IP address, with fallback chain:

1. CloudFlare: cf-connecting-ip header (if behind CloudFlare)
2. X-Forwarded-For: x-forwarded-for header (if behind proxy, uses first IP)
3. X-Real-IP: x-real-ip header (if behind nginx/Apache)
4. Connection IP: Direct connection IP (development only)
5. Fallback: 'unknown' (should not occur in production)

Architecture

InMemoryRateLimitStore

Single-instance in-memory storage suitable for:

• ✅ Development environments
• ✅ Single-instance deployments
• ✅ Testing environments

Not suitable for:

• ❌ Multi-instance deployments (each instance has separate store)
• ❌ Kubernetes clusters
• ❌ Serverless (no state persistence between requests)

Future: Redis Adapter

For production multi-instance deployments, implement a Redis adapter:

// Example: Redis-backed rate limiter (not yet implemented)
const store = createRedisRateLimitStore({
  redis: RedisClient.from(process.env.REDIS_URL),
  prefix: 'ratelimit:',
})

This would allow sharing rate limit state across instances.

Customization

Create Custom Rate Limiter

import { createRateLimiter } from '@/lib/middleware'

// Rate limit per user instead of IP
const userLimiter = createRateLimiter({
  limit: 100,
  window: 60 * 1000,
  keyGenerator: (request) => {
    const userId = extractUserIdFromRequest(request)
    return `user:${userId}`
  }
})

export async function POST(request: NextRequest) {
  const limitResponse = userLimiter(request)
  if (limitResponse) return limitResponse
  // ...
}

Adjust Rate Limits

Edit the rate limit configuration in rate-limit.ts:

export const rateLimiters = {
  login: createRateLimiter({
    limit: 5,        // Change this to adjust max attempts
    window: 60 * 1000, // Change this to adjust time window
  }),
  // ... other limiters
}

Custom Error Responses

const customLimiter = createRateLimiter({
  limit: 5,
  window: 60 * 1000,
  onLimitExceeded: (key, request) => {
    return new Response(
      JSON.stringify({
        error: 'Too many login attempts',
        message: 'Please try again in 1 minute',
        retryAt: new Date(Date.now() + 60000).toISOString(),
      }),
      {
        status: 429,
        headers: { 'Content-Type': 'application/json' },
      }
    )
  },
})

Monitoring & Debugging

Get Rate Limit Status

import { getRateLimitStatus } from '@/lib/middleware'

export async function GET(request: NextRequest) {
  const status = getRateLimitStatus(request, 'login')

  console.log(`Login attempts: ${status.current}/${status.limit}`)
  console.log(`Remaining: ${status.remaining}`)
}

Reset Rate Limit

import { resetRateLimit } from '@/lib/middleware'

// Reset rate limit for an IP (admin operation)
resetRateLimit('192.168.1.100')

Debug in Development

// Enable detailed logging in development
if (process.env.NODE_ENV === 'development') {
  console.log(`Rate limit check: ${endpointType}`)
  console.log(`IP: ${getClientIp(request)}`)
  console.log(`Current count: ${store.get(key)}`)
}

Testing Rate Limits

Manual Testing (Unix/Linux/Mac)

# Test login rate limiting (should fail on 6th request)
for i in {1..10}; do
  echo "Attempt $i:"
  curl -X POST http://localhost:3000/api/v1/default/auth/login \
    -H "Content-Type: application/json" \
    -d '{"username":"test","password":"test"}' \
    -w "Status: %{http_code}\n\n"
  sleep 0.5
done

Manual Testing (Windows PowerShell)

# Test login rate limiting
for ($i=1; $i -le 10; $i++) {
  Write-Host "Attempt $i:"
  $response = Invoke-WebRequest -Uri "http://localhost:3000/api/v1/default/auth/login" `
    -Method Post `
    -Headers @{"Content-Type"="application/json"} `
    -Body '{"username":"test","password":"test"}' `
    -SkipHttpErrorCheck
  Write-Host "Status: $($response.StatusCode)`n"
  Start-Sleep -Milliseconds 500
}

Expected Results

• Requests 1-5: Status 200 or other (depending on endpoint logic)
• Request 6+: Status 429 Too Many Requests

Performance Impact

Memory Usage

• Per IP: ~24 bytes (for entry + overhead)
• With 10,000 unique IPs: ~240 KB
• Automatic cleanup: Expired entries removed every 60 seconds

Latency

• Rate limit check: < 1ms (hash map lookup)
• No external service calls (in-memory store)
• Negligible performance impact

Security Considerations

Strengths

✅ Prevents brute-force attacks (5 attempts/min on login) ✅ Prevents user enumeration (register limited to 3/min) ✅ Prevents API scraping (100 requests/min on GET) ✅ Prevents DoS on bootstrap (1/hour) ✅ IP-based (resistant to distributed attacks from same IP)

Limitations

⚠️ Single-instance only (not suitable for multi-instance without Redis) ⚠️ Memory-based (lost on restart) ⚠️ No cross-IP distributed attack protection ⚠️ No captcha integration ⚠️ No account lockout (only per-IP, not per-account)

Production Recommendations

For production deployments:

1. Implement Redis adapter for distributed rate limiting
2. Add captcha after 3 failed login attempts
3. Add account lockout logic (contact support flow)
4. Monitor 429 responses in error tracking (Sentry)
5. Alert on rate limit spikes (potential attack)
6. Whitelist trusted IPs if needed (admin dashboards, monitoring systems)

Troubleshooting

Rate limiting too strict?

Increase limits or time window:

login: createRateLimiter({
  limit: 10,        // Increased from 5
  window: 120 * 1000, // Increased to 2 minutes
})

Rate limiting not working?

Check:

1. Middleware is imported and called
2. Check request headers (IP detection may fail)
3. Check browser console for 429 responses
4. Enable debug logging

Wrong IP detected?

Verify proxy headers:

// Add logging in getClientIp()
console.log('CF IP:', request.headers.get('cf-connecting-ip'))
console.log('X-Forwarded-For:', request.headers.get('x-forwarded-for'))

Future Enhancements

Planned

• Redis adapter for distributed rate limiting
• Captcha integration after N failures
• Account-level lockout (not just IP)
• Dynamic rate limits based on threat level
• Rate limit analytics and dashboard
• User-friendly error pages with countdown timer

Consider

• Sliding window vs fixed window (currently sliding)
• Token bucket algorithm for smoother limits
• ML-based anomaly detection
• Integration with WAF (Web Application Firewall)

References

• Implementation: frontends/nextjs/src/lib/middleware/rate-limit.ts
• Main API Route: frontends/nextjs/src/app/api/v1/[...slug]/route.ts
• Bootstrap Route: frontends/nextjs/src/app/api/bootstrap/route.ts
• NIST Guidelines: Rate Limiting Best Practices

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Last Updated: 2026-01-21 Status: Production Ready (Single-Instance) Next: Implement Redis adapter for multi-instance deployments