All 7 Rate Limiting with Redis questions
More in Rate Limiting with Redis
How do you implement a basic fixed window rate limiter using Redis's INCR and EXPIRE commands? What is the sliding window log algorithm for rate limiting, and how can it be implemented using a Redis sorted set? What is the token bucket algorithm for rate limiting, and what advantage does it offer over a simple fixed window counter? How do you provide helpful feedback to API consumers about their current rate limit status, such as how many requests they have remaining? How would you implement a distributed rate limiter using Redis that works correctly across multiple application servers handling requests for the same user? How would you design a tiered rate limiting system that applies different limits based on a user's subscription plan?
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Redis › Rate Limiting with Redis

What is rate limiting, and why is Redis a good fit for implementing it?

Beginner

Answer

Rate limiting restricts how many times a specific action, such as an API call, can happen within a given time period, and Redis is well suited for this because its fast, atomic counter operations and automatic key expiration let you accurately track and enforce these limits with very low latency, even under high traffic.
INCR api_calls:user123
EXPIRE api_calls:user123 60
Real-world example An API gateway limits each customer to one hundred requests per minute, using a Redis counter that increments with every request and automatically resets every sixty seconds thanks to the key's expiration.

Common follow-ups: What happens if the increment and expire commands are not executed atomically together?;How do you choose an appropriate time window for a specific rate limit?

Lua Scripting;Expiration & Eviction
All 7 Rate Limiting with Redis questions