Requirements

Functional Requirements:

• per-user / per-API rate limits.
• Admins can add/update/delete/view rate-limit rules via an API or console.

Non-Functional Requirements:

• Should have a high fault tolerance
• Should have low latency
• Exception handling

API Design

ID <- key for the IP address/user ID/ or whatever we want to rate limit on

Token Amount <- the amount of tokens left in the bucket for this user

Token Refresh <- the amount of tokens that get added every second/minute/etc

High-Level Design

There is a rate limit API gateway between the client and the server that if successful, lets you hit the server with the request. There is a Redis cache that the API gateway reads from to see if the request will succeed or not.

Detailed Component Design

Deep dive into 2-3 key components. Explain how they work, how they scale, discuss tradeoffs, capacity, and any relevant algorithms or data structures.