Rate Limits

X-RateLimit-Limit: 50
X-RateLimit-Remaining: 47
X-RateLimit-Reset: 1703155200

class RateLimitedClient {
  constructor(apiKey) {
    this.apiKey = apiKey;
    this.remaining = 50;
    this.resetAt = 0;
  }

  async request(url, options) {
    // Wait if we're out of quota
    if (this.remaining <= 0 && Date.now() < this.resetAt) {
      const delay = this.resetAt - Date.now();
      await sleep(delay);
    }

    const response = await fetch(url, {
      ...options,
      headers: {
        ...options.headers,
        'X-API-Key': this.apiKey
      }
    });

    // Update rate limit state
    this.remaining = parseInt(response.headers.get('X-RateLimit-Remaining'));
    this.resetAt = parseInt(response.headers.get('X-RateLimit-Reset')) * 1000;

    return response;
  }
}

async function requestWithRetry(url, options, maxRetries = 3) {
  for (let attempt = 0; attempt < maxRetries; attempt++) {
    const response = await fetch(url, options);
    
    if (response.status === 429) {
      const retryAfter = response.headers.get('Retry-After') || 
                         response.headers.get('X-RateLimit-Reset');
      const delay = retryAfter 
        ? parseInt(retryAfter) * 1000 
        : Math.pow(2, attempt) * 1000;
      
      console.log(`Rate limited. Waiting ${delay}ms...`);
      await sleep(delay);
      continue;
    }
    
    return response;
  }
  
  throw new Error('Max retries exceeded');
}

// ❌ Bad: N requests for N parcels
for (const trackingNumber of trackingNumbers) {
  await fetch(`/api/v1/tracking/${trackingNumber}`);
}

// ✅ Good: 1 request for N parcels
await fetch('/api/v1/tracking/batch', {
  method: 'POST',
  body: JSON.stringify({ trackingNumbers })
});