Intermediate LevelSystem Design & Architecture
How do you design a Distributed Rate Limiter using Redis Lua Scripts?
❓ Interview Prompt: Explain Distributed Rate Limiting, Sliding Window Log vs Counter, atomic Redis Lua scripts, and API Gateway integration.
Enforcing rate limits across a cluster of API Gateway nodes requires a shared distributed cache (Redis):
Atomic Redis Lua Execution:
Checking and incrementing request counters must happen atomically to prevent race conditions across gateway replicas. Executing a Redis Lua Script guarantees that counter evaluation runs atomically on the Redis server!
Code Implementation Example
typescript
const slidingWindowLua = '
local key = KEYS[1]
local now = tonumber(ARGV[1])
local window = tonumber(ARGV[2])
local limit = tonumber(ARGV[3])
redis.call('ZREMRANGEBYSCORE', key, 0, now - window)
local current = redis.call('ZCARD', key)
if current < limit then
redis.call('ZADD', key, now, now)
return 1
end
return 0
';💡Atomic Sliding Window Rate Limiter Lua Script for Redis.
🎯 Interview Key Takeaway
Use atomic Redis Lua scripts to execute sliding window rate limiting across distributed API Gateway nodes without race conditions.
#System Design#Rate Limiter#Redis Lua#Distributed Systems#Intermediate
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