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Fail open and fail closed

What a limiter does when its shared store is down: let everything through, or refuse everything.

Taught in Chapter 10: Rate Limiting.

More from the same chapter

• Fixed window: Counts requests per calendar second or minute; simple, but lets up to twice the limit through at a boundary.
• HTTP 429: Too Many Requests: the answer to a caller over its rate limit, usually with a Retry-After header.
• Leaky bucket: A rate limiter that queues requests and lets them out at a fixed rate, refusing only when the queue is full.
• Rate limiter: Caps how many requests each caller may send, refusing the rest at once with HTTP 429.
• Sliding window: Counts the requests in the last full window wherever it ends, so no span holds more than the limit.
• Token bucket: A rate-limiting algorithm: tokens refill at the limit, each request takes one, and the bucket size allows short bursts.