## Rate Limiting

### Simple In-Memory Rate Limiter

```typescript
class RateLimiter {
  private requests = new Map<string, number[]>()

  async checkLimit(
    identifier: string,
    maxRequests: number,
    windowMs: number
  ): Promise<boolean> {
    const now = Date.now()
    const requests = this.requests.get(identifier) || []

    // Remove old requests outside window
    const recentRequests = requests.filter(time => now - time < windowMs)

    if (recentRequests.length >= maxRequests) {
      return false  // Rate limit exceeded
    }

    // Add current request
    recentRequests.push(now)
    this.requests.set(identifier, recentRequests)

    return true
  }
}

const limiter = new RateLimiter()

export async function GET(request: Request) {
  const ip = request.headers.get('x-forwarded-for') || 'unknown'

  const allowed = await limiter.checkLimit(ip, 100, 60000)  // 100 req/min

  if (!allowed) {
    return NextResponse.json({
      error: 'Rate limit exceeded'
    }, { status: 429 })
  }

  // Continue with request
}
```