System design interview question
Design a Distributed Rate Limiting Service for API Gateway (like AWS API Gateway throttling)
Design a distributed rate limiting service that enforces API quotas across a global infrastructure serving 500M requests per day with traffic originating from 50+ regions. The system must support multiple rate limiting algorithms (token bucket, sliding window, leaky bucket), handle 100K concurrent users, and make sub-millisecond limiting decisions with 99.99% accuracy. Requests must be rate-limited consistently across distributed API gateway instances, handle burst traffic gracefully, and support dynamic quota updates without service restarts. The system needs to track usage metrics, provide analytics dashboards, and ensure fairness when enforcing limits across different customer tiers.
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