The Art of CTO API Rate Limit Planner helps engineers design rate limiting strategies with quota calculations, burst handling, and throttling algorithms for API gateway configuration.
Frequently Asked Questions
What rate limiting algorithm should I use for my API?
The four main algorithms are fixed window (simplest, but allows burst at window boundaries), sliding window (smoother distribution, slightly more complex), token bucket (allows controlled bursts while maintaining average rate — best for most APIs), and leaky bucket (strictly smooth output, good for upstream protection). Token bucket is the most popular choice for public APIs because it accommodates legitimate traffic bursts while preventing abuse. For internal microservices, sliding window counters provide a good balance of accuracy and simplicity.
How do you set appropriate API rate limits?
Base rate limits on your infrastructure capacity divided by the number of expected consumers, with a safety margin of 20-30%. Analyze actual usage patterns to understand p50, p95, and p99 request volumes per client. Set burst limits at 2-5x the sustained rate to accommodate legitimate spikes. Implement tiered limits based on plan level (free, pro, enterprise) and communicate limits clearly via response headers (X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset). Start generous and tighten based on observed abuse patterns.