What is Rate Limiting

Definition

Rate limiting is a control that caps how many requests a client can make to a service within a time window, protecting the service from overload, abuse, and runaway costs while ensuring fair access among many consumers.

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Protects services from overload and denial-of-service abuse
Ensures fair resource sharing among many clients
Controls costs by capping expensive API or compute usage
Improves stability by smoothing traffic spikes

Real World Example

An API provider applies rate limiting of 100 requests per minute per key, so a misbehaving client cannot overwhelm the service or rack up huge costs, while legitimate users continue unaffected.

FAQs

Why is rate limiting important?

It prevents overload and abuse, ensures fair access, and controls costs by capping how often clients can call a service.

What algorithms implement rate limiting?

Token bucket, leaky bucket, and fixed or sliding window counters are common rate-limiting algorithms.

What happens when a limit is exceeded?

Requests are typically rejected with a 429 status and a retry-after hint, asking the client to slow down.