Performing an action via a callback is fairly easy and doable. Sometimes requirement may be a bit enhance that we need to track every change now and then. On the same note, if we have associations and we wanted to make some changes that needs to be reflected on previous and new values, this dirty concepts can save our time. This module gives a way to track changes done in an active-record object. By default, rails include ActiveRecord::Dirty this module. This gives many powerful methods that helps us to track attribute changes. This methods are based on the attribute

How does Unicorn works out? Unicorn works in cluster wherein it queues requests to multiple workers. Whenever the Unicorn master starts, it loads the app into its memory and handles to serve the requests to its workers. Here is a link which will elaborate the architecture for Unicorn in a nutshell: [Unicorn Architecture(https://github.com/blog/517-unicorn)][1] This is one of the good architecture that helps to distribute requests to provide load balancing. At the same time, there might occur an issue with Data Transaction (Concurrency). Would like to give a small scenario that created a issue in