Rate Limiting
Rate limiting restricts the number of requests a client can make to a server within a given time window. It is a fundamental defense against brute-force attacks, scraping, and API abuse.
What Is Rate Limiting?
Rate limiting is a technique that controls how many requests a client can make to a server within a specified time period. When a client exceeds the allowed rate, subsequent requests are rejected (typically with an HTTP 429 "Too Many Requests" response) or throttled. Rate limiting is one of the most fundamental defenses against automated abuse, protecting both application logic and server resources.
Common Rate Limiting Algorithms
- Fixed window: Allows N requests per time window (e.g., 100 requests per minute). Simple but can allow bursts at window boundaries.
- Sliding window: Smooths the fixed window approach by considering the overlap between adjacent windows.
- Token bucket: Tokens are added to a bucket at a fixed rate; each request consumes a token. Allows short bursts while enforcing an average rate.
- Leaky bucket: Requests are processed at a constant rate regardless of arrival pattern, smoothing traffic flow.
Challenges with Rate Limiting
Simple IP-based rate limiting is easily circumvented by attackers using backconnect proxies that rotate IPs on each request. If an attacker has access to a pool of thousands of residential proxies, each IP may only make a handful of requests, staying well within rate limits while the aggregate attack is massive. This is why rate limiting must be combined with other signals.
Smarter Rate Limiting with AntiProxies
By integrating AntiProxies IP reputation data into your rate limiting logic, you can apply different thresholds based on connection risk. Traffic from clean residential IPs might get a generous limit, while traffic from known proxies, VPNs, or datacenter IPs gets a stricter limit. This tiered approach provides stronger protection against credential stuffing and scraping without impacting the experience for normal users.