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Grokking Modern System Design Interview

Design of a Rate Limiter

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High-level design

A rate limiter is a dedicated service that sits between the client and the web server. It evaluates incoming requests against defined rules to decide whether to forward them to the server or block them. The figure below illustrates this interaction. Lyft’s rate-limiting service provides a practical example of how these rules are structured.

YAML
domain: messaging
descriptors:
   -key: message_type
    value: marketing
    rate_limit:
               unit: day
               request_per_unit: 5

In this example, the unit is set to day and request_per_unit is 5. This rule limits the client to five marketing messages per day.

A request with ID 101, received by one of the web servers
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A request with ID 101, received by one of the web servers

Detailed design

The high-level design leaves key questions unanswered:

  • Where are the rules stored? ...