How do you implement Redis Lua scripting for atomic operations?

Lua scripts execute atomically on Redis server: **Basic Script Execution:** # Simple Lua script EVAL "return redis.call('SET', KEYS[1], ARGV[1])" 1 mykey myvalue # Get and increment atomically EVAL "local val = redis.call('GET', KEYS[1]) or 0; redis.call('SET', KEYS[1], val + ARGV[1]); return val + ARGV[1]" 1 counter 5 **Script Caching:** # Load script and get SHA SCRIPT LOAD "return redis.call('GET', KEYS[1])" # Returns: "6b1bf486c81ceb7edf3c093f4c48582e38c0e791" # Execute by SHA EVALSHA 6b1bf486c81ceb7edf3c093f4c48582e38c0e791 1 mykey **Complex Example - Rate Limiting:** -- rate_limit.lua local key = KEYS[1] local window = tonumber(ARGV[1]) local limit = tonumber(ARGV[2]) local current_time = tonumber(ARGV[3]) -- Clean old entries redis.call('ZREMRANGEBYSCORE', key, 0, current_time - window) -- Count current requests local current_requests = redis.call('ZCARD', key) if current_requests < limit then -- Add current request redis.call('ZADD', key, current_time, current_time) redis.call('EXPIRE', key, window) return {1, limit - current_requests - 1} else return {0, 0} end **Python Usage:** rate_limit_script = r.register_script(open('rate_limit.lua').read()) # Check rate limit (100 requests per 60 seconds) result = rate_limit_script( keys=['user:123:requests'], args=[60, 100, int(time.time())] ) allowed, remaining = result if allowed: print(f"Request allowed. {remaining} remaining") else: print("Rate limit exceeded") **Benefits:** • Atomic execution • Reduced network traffic • Server-side logic • Better performance for complex operations