HTTP 429 Too Many Requests

What It Means

The HTTP 429 Too Many Requests status code indicates that you've sent too many requests in a given time window. The server is rate limiting your requests to protect itself from abuse or overload.

Example Response

HTTP/1.1 429 Too Many Requests
Retry-After: 60
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 0
X-RateLimit-Reset: 1705320000
Content-Type: application/json

{
  "error": "Too Many Requests",
  "message": "Rate limit exceeded. Try again in 60 seconds."
}

Common Rate Limit Headers

How to Handle 429s

async function fetchWithRateLimit(url) {
  const response = await fetch(url);

  if (response.status === 429) {
    // Get retry delay from header (or default to 60s)
    const retryAfter = response.headers.get('Retry-After') || 60;
    console.log(`Rate limited. Waiting ${retryAfter}s...`);

    await new Promise(r => setTimeout(r, retryAfter * 1000));
    return fetchWithRateLimit(url); // Retry
  }

  return response;
}

Exponential Backoff

async function fetchWithBackoff(url, attempt = 0) {
  const response = await fetch(url);

  if (response.status === 429 && attempt < 5) {
    // Exponential backoff: 1s, 2s, 4s, 8s, 16s
    const delay = Math.pow(2, attempt) * 1000;
    const jitter = Math.random() * 1000; // Add randomness
    await new Promise(r => setTimeout(r, delay + jitter));
    return fetchWithBackoff(url, attempt + 1);
  }

  return response;
}

Rate Limiting Strategies

Best Practices

• Always respect Retry-After headers
• Implement exponential backoff with jitter
• Cache responses to reduce API calls
• Use webhooks instead of polling when available
• Batch requests when the API supports it
• Monitor your rate limit headers proactively

Server Implementation

Express.js with express-rate-limit

const rateLimit = require('express-rate-limit');

const limiter = rateLimit({
  windowMs: 60 * 1000, // 1 minute
  max: 100, // 100 requests per minute
  standardHeaders: true, // Return rate limit info
  handler: (req, res) => {
    res.status(429).json({
      error: 'Too Many Requests',
      retryAfter: Math.ceil(req.rateLimit.resetTime / 1000)
    });
  }
});

app.use('/api/', limiter);