System Requirements
- Support customizable limits per IP, User ID, and API Key
- Sub-2ms check latency with distributed synchronization
- Graceful degradation to allow traffic if rate limiter cluster fails (fail-open)
- Return HTTP 429 Too Many Requests with Retry-After header
Graded Constraints
01Cost within $1,200/month
02Edge Reverse Proxy or API Gateway connected to distributed cache
03In-memory store (Redis / Memcached) for sliding window timestamps
04Centralized rule storage (Database) for policy configuration
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