Purpose
A rate limiter controls the rate of requests that a client can send to an API. It prevents DoS attacks, reduces costs, and ensures fair usage.
Common Rate Limiting Algorithms
1. Token Bucket
- •Tokens are added at a fixed rate
- •Each request consumes one token
- •Allows burst traffic up to bucket capacity
2. Leaking Bucket
- •Requests are added to a queue (bucket)
- •Processed at a fixed rate
- •Overflow requests are dropped
3. Fixed Window Counter
- •Time divided into fixed windows
- •Counter reset at the start of each window
- •Simple but can allow 2x the rate at window boundaries
4. Sliding Window Log
- •Tracks timestamps of all requests
- •Remove entries older than the window size
- •Accurate but memory-intensive
5. Sliding Window Counter
- •Hybrid of fixed window + sliding window
- •Approximates sliding window with less memory
