API Rate Limiting

Key Definitions

• Rate Limit: The maximum number of API requests allowed in a specific time frame.
• Throttling: A method of controlling the rate at which requests are processed.
• Bucket Algorithm: A technique that uses "buckets" to manage request counts over time.

Implementing Rate Limiting

Follow these steps to implement API rate limiting:

1. Determine the appropriate rate limit for your API (e.g., 100 requests per hour).
2. Choose a rate limiting algorithm (e.g., fixed window, sliding window, token bucket).
3. Implement the chosen algorithm in your API gateway or service.
4. Return appropriate HTTP status codes (e.g., 429 Too Many Requests) when limits are exceeded.
5. Log rate limiting events for monitoring and analysis.

Code Example

            const rateLimit = (limit, timeFrame) => {
                let requests = {};
                return (req, res, next) => {
                    const key = req.ip; // or use req.user.id
                    const currentTime = Date.now();
                    if (!requests[key]) {
                        requests[key] = { count: 1, start: currentTime };
                    } else {
                        if (currentTime - requests[key].start < timeFrame) {
                            requests[key].count++;
                        } else {
                            requests[key].count = 1;
                            requests[key].start = currentTime;
                        }
                    }
                    if (requests[key].count > limit) {
                        res.status(429).send('Too Many Requests');
                    } else {
                        next();
                    }
                };
            };
            

Recommendations

• Use exponential backoff for retrying requests after hitting rate limits.
• Communicate rate limits through response headers (e.g., X-RateLimit-Limit).
• Consider user-specific quotas rather than global limits for more flexibility.
• Monitor usage patterns to adjust rate limits dynamically.