Design a Distributed Rate Limiter
Company: OpenAI
Role: Software Engineer
Category: System Design
Interview Round: Technical Screen
Design a distributed rate limiting system for a large API platform.
The platform has many API gateways and backend services running across multiple regions. The rate limiter must decide, for each incoming request, whether it should be allowed or rejected based on configurable limits such as:
- Requests per second per user, API key, tenant, IP address, or endpoint.
- Different limits for different subscription tiers.
- Burst handling.
- Dynamic configuration updates.
Assume the platform serves up to 1 million requests per second globally, with most checks needing to complete in a few milliseconds. The design should cover the request flow, APIs, data model, rate limiting algorithm, distributed coordination, consistency trade-offs, failure handling, scalability, and observability.
Quick Answer: This question evaluates competency in distributed systems architecture, API and data model design, performance engineering, and operational concerns such as rate limiting algorithms, consistency trade-offs, distributed coordination, failure handling, scalability, and observability.