Requirements of a Rate Limiter’s Design


Our focus in this lesson is to design a rate limiter with the following functional and non-functional requirements.

Functional requirements

  • To limit the number of requests a client can send to an API within a time window.
  • To make the limit of requests per window configurable.
  • To make sure that the client gets a message (error or notification) whenever the defined threshold is crossed within a single server or combination of servers.

Non-functional requirements

  • Availability: Essentially, the rate limiter protects our system. Therefore, it should be highly available.
  • Low latency: Because all API requests pass through the rate limiter, it should work with a minimum latency without affecting the user experience.
  • Scalability: Our design should be highly scalable. It should be able to rate limit an increasing number of clients’ requests over time.

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