This topic is about using Redis and LUA script in Rails. Before proceeding, you may like to read [ Introduction to LUA script with Redis][1] Redis doesn't have any command to calculate total number of keys We'll use [zrangebyscore][2] to find number of members between index range. Instal [redis-rb][3] Start rails console Prepare a dataset based on timestamp > t10 = 10.minutes.ago => 1386935151 > t20 = 20.minutes.ago => 1386934568 > t30 = 30.minutes.ago => 1386933971 > t40 = 40.minutes.ago => 1386933374 This is non-realistic data, may vary for you. Populate redis with Sorted Set > redis = Redis.new # initialize redis => # zadd -

What is Redis ? We all might be familiar with [Redis][1] . For those who are not - It's a "NoSQL" key-value data store. More precisely, it is a data structure server. To read more - [Redis-Wiki][2] Do [try redis][3] it has a nice interactive tutorial. To install and setup redis on your machine see [how-to-install-and-use-redis][4] What is LUA ? LUA is an embeddable scripting language. About LUA - http://www.lua.org/about.html Redis >= 2.6 supports embedded scripting language. Lets give a try to it. To run a script in redis we need