Rate Limiting Tutorial
Protect APIs from overload and abuse: algorithms, Redis-backed limits and policy design
Intermediate4 lessonsabout 24 min of reading
This course is for backend developers and system design candidates who know what an API is and have, sooner or later, watched one fall over because a single client sent too much traffic. You should be comfortable reading short Python programs. No special infrastructure is needed: every algorithm is implemented from scratch and driven by a simulated clock, so the printed results are exactly reproducible on your machine.
You will learn where limits belong in a system and what to key them on, how the four classic algorithms (fixed window, sliding window, token bucket, leaky bucket) behave on the same traffic, how to make a limit hold across many servers using Redis without race conditions, what a good 429 response looks like, and how to write a policy that is fair to honest users while still slowing down abuse.
The lessons run from why to how to scale to policy. The first covers the purpose and placement of limits, the second the algorithms, the third the distributed version, and the last the human decisions around numbers, bursts and fairness. Related background lives in Redis and System Design.
Rate Limiting lessons
- 1Rate Limiting Explained: Why, Where and What to LimitLearn why APIs need rate limiting, where to enforce it (edge, gateway, service) and whether to key limits by IP, user or API key, with a runnable example.6 min read
- 2Rate Limiting Algorithms: Token Bucket, Leaky Bucket and Sliding WindowCompare fixed window, sliding window, token bucket and leaky bucket rate limiting algorithms with runnable Python code and simulated clocks.6 min read
- 3Distributed Rate Limiting with Redis, 429 Responses and Retry-AfterMake rate limits work across many servers: Redis counters, Lua scripts, race conditions, fail-open choices, plus 429 and Retry-After headers done right.6 min read
- 4Designing Rate Limit Policies: Bursts, Fairness and Abuse HandlingDesign rate limit policies: choose numbers, burst sizes and tiers, protect small tenants from heavy ones, and handle abuse and client retries sensibly.6 min read
Preparing for an interview? Practise System Design interview questions
Learning Rate Limiting to land a job? Browse open roles or check which skills are trending.