Senior LevelNode JS

How do you implement distributed Token Bucket rate limiting in Node.js using atomic Redis Lua scripts?

❓ Interview Prompt: Explain distributed Rate Limiting, Token Bucket / Leaky Bucket algorithms, atomic Redis Lua script execution, and race condition prevention.

Rate limiting across distributed Node.js microservices requires atomic state evaluation:

Why Redis Lua Scripts?

Executing Token Bucket logic inside a single Redis Lua script guarantees single-threaded atomic evaluation in Redis memory, eliminating race conditions when 10,000 concurrent Node.js requests hit the rate limiter!

Code Implementation Example

javascript

const luaRateLimiterScript = '
  local key = KEYS[1]
  local limit = tonumber(ARGV[1])
  local current = tonumber(redis.call('get', key) or "0")
  if current + 1 > limit then return 0 else
    redis.call("INCRBY", key, 1)
    redis.call("EXPIRE", key, 60)
    return 1
  end
';

💡Atomic Token Bucket rate limiting via Redis Lua script.

🎯 Interview Key Takeaway

Execute rate limiting logic in atomic Redis Lua scripts to prevent distributed race conditions.

#Rate Limiting#Token Bucket#Redis Lua#Senior

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