API Rate Limiting

Table of Contents

• Overview
• When to Use
• Quick Start
• Reference Guides
• Best Practices

Overview

Protect APIs from abuse and manage traffic using various rate limiting algorithms with per-user, per-IP, and per-endpoint strategies.

When to Use

• Protecting APIs from brute force attacks
• Managing traffic spikes
• Implementing tiered service plans
• Preventing DoS attacks
• Fairness in resource allocation
• Enforcing quotas and usage limits

Quick Start

Minimal working example:

// Token Bucket Rate Limiter
class TokenBucket {
  constructor(capacity, refillRate) {
    this.capacity = capacity;
    this.tokens = capacity;
    this.refillRate = refillRate; // tokens per second
    this.lastRefillTime = Date.now();
  }

  refill() {
    const now = Date.now();
    const timePassed = (now - this.lastRefillTime) / 1000;
    const tokensToAdd = timePassed * this.refillRate;

    this.tokens = Math.min(this.capacity, this.tokens + tokensToAdd);
    this.lastRefillTime = now;
  }

  consume(tokens = 1) {
    this.refill();

    if (this.tokens >= tokens) {
      this.tokens -= tokens;
      return true;
    }
// ... (see reference guides for full implementation)

Reference Guides

Detailed implementations in the references/ directory:

Guide	Contents
Token Bucket Algorithm	Token Bucket Algorithm
Sliding Window Algorithm	Sliding Window Algorithm
Redis-Based Rate Limiting	Redis-Based Rate Limiting
Tiered Rate Limiting	Tiered Rate Limiting
Python Rate Limiting (Flask)	Python Rate Limiting (Flask)
Response Headers	Response Headers

Best Practices

✅ DO

• Include rate limit headers in responses
• Use Redis for distributed rate limiting
• Implement tiered limits for different user plans
• Set appropriate window sizes and limits
• Monitor rate limit metrics
• Provide clear retry guidance
• Document rate limits in API docs
• Test under high load

❌ DON'T

• Use in-memory storage in production
• Set limits too restrictively
• Forget to include Retry-After header
• Ignore distributed scenarios
• Make rate limits public (security)
• Use simple counters for distributed systems
• Forget cleanup of old data