Rate Limiter
Difficulty: Medium
What It Tests
Algorithmic rate limiting, distributed enforcement, Redis patterns.
Topics Covered
Hello Interview Breakdown
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Video Walkthroughs
Approach Hints
- Sliding window counter using Redis INCR + EXPIRE
- Atomic Lua script to check-and-increment in one round trip
- Store limit config in a centralized config store
- Return Retry-After header on 429 responses; handle Redis failure with a local in-memory fallback counter