Bits of .NET

The Pattern

async function fetchWithRetry(url, options = {}, maxRetries = 3) {
  for (let i = 0; i <= maxRetries; i++) {
    try {
      const response = await fetch(url, options);
      
      // Success
      if (response.ok) {
        return await response.json();
      }
      
      // Server error (5xx) or rate limit (429) - retry
      if (response.status >= 500 || response.status === 429) {
        if (i === maxRetries) throw new Error('Max retries reached');
        
        // Exponential backoff: 1s, 2s, 4s, 8s...
        const delay = Math.pow(2, i) * 1000;
        console.log(`Retry ${i + 1} after ${delay}ms`);
        await new Promise(resolve => setTimeout(resolve, delay));
        continue;
      }
      
      // Client error (4xx) - don't retry
      throw new Error(`HTTP ${response.status}`);
      
    } catch (error) {
      if (i === maxRetries) throw error;
      
      // Network error - retry with backoff
      const delay = Math.pow(2, i) * 1000;
      await new Promise(resolve => setTimeout(resolve, delay));
    }
  }
}

// Usage
try {
  const data = await fetchWithRetry('/api/data');
  console.log(data);
} catch (error) {
  console.error('Request failed after retries:', error);
}

// Add randomness to prevent thundering herd
const delay = Math.pow(2, i) * 1000;
const jitter = Math.random() * 1000;
await new Promise(resolve => setTimeout(resolve, delay + jitter));

“API went down during peak traffic. Exponential backoff prevented retry storm from making it worse. Users saw loading states instead of errors. Service recovered gracefully.”