Design Rate Limiter

A standalone rate limiter service for Java Spring Boot applications that supports multiple rate limiting algorithms and can be used as a separate service to control API request rates.

Demo

High Level Design

Class Diagram

Features

• Multiple rate limiting algorithms supported:
  • Token Bucket
  • Leaking Bucket
  • Fixed Window Counter
• Redis-based storage.
• Dynamic rule loading from DOC files.
• Scheduled rule reloading (every 1 hour).
• REST API for rate limit checking and rule management.
• Standalone service architecture.

Integration with Application

@Service
public class ApiGatewayService {
    
    @Autowired
    private RestTemplate restTemplate;
    
    @Value("${rate.limiter.url}")
    private String rateLimiterUrl;
    
    public boolean isRequestAllowed(String apiPath, String method, String clientId) {
        String resourceId = apiPath + ":" + method;
        
        RateLimitRequest request = new RateLimitRequest(resourceId, clientId);
        
        try {
            ResponseEntity<RateLimitResponse> response = restTemplate.postForEntity(
                rateLimiterUrl + "/check", request, RateLimitResponse.class);
                
            return response.getBody().isAllowed();
        } catch (HttpClientErrorException.TooManyRequests ex) {
            return false;
        }
    }
}

Rate Limit Rules Format

API: /api/users
METHOD: GET
ALGORITHM: TOKEN_BUCKET
LIMIT: 100
PERIOD: 60
TIME_UNIT: SECONDS

API: /api/orders
METHOD: POST
ALGORITHM: LEAKING_BUCKET
LIMIT: 30
PERIOD: 60
TIME_UNIT: SECONDS

API Usage

• Check Rate Limit

  POST /rate-limiter/api/v1/rate-limit/check
  
  //Request Body:
  {
  "resourceId": "/api/users:GET",
  "clientId": "user123"
  }
  
  //Response:
  {
  "allowed": true,
  "limit": 100,
  "remaining": 99,
  "resetTime": 1646324568
  }

• Get All Rules

  GET /rate-limiter/api/v1/rate-limit/rules

• Reload Rules

  POST /rate-limiter/api/v1/rate-limit/rules/reload