限流基本概念

Let's learn the vocabulary of rate limiting: request quotas, time windows, and what happens when a client sends too many requests.

A request quota is the max number of requests an API lets you make — the how many of a rate limit, protecting the API from overload.

If your quota is 100, request 101 is blocked. The quota is your hard ceiling, regardless of how fast or slow you send them.

A time window is the period your quota applies to — the per what part. Like a library loan, the count resets when the window ends.

Combine a quota with a time window and you have a full rate limit: how many requests, in what period — for example, 100 per minute.

Behind the scenes the API counts your requests in the current window. Once the counter hits the quota, further requests get blocked.

Exceed your quota inside the window and the API rejects the request rather than processing it — vital so no one floods the service.

A rejected, rate-limited request returns HTTP 429 Too Many Requests — the standard way an API says slow down, you've hit your limit.

A 429 often ships with a Retry-After header telling you exactly how long to wait — a number of seconds or a specific date.

As an API consumer, handle limits gracefully: recognize 429s, respect Retry-After, and wait before retrying instead of hammering away.

Which of the following are fundamental concepts related to basic API rate limiting?

Recap: a request quota plus a time window makes a rate limit; exceeding it returns HTTP 429, and Retry-After tells you when to try again.