My curiosity dragged me to find what is the stack, that Stack Overflow is based on, caching in particular. And the site here , gave description of how things are build up. But this gives the deployment knowledge of items , the hardware and software in use and how they are organized.But not how a particular feature is designed for example the badge allocation, We can see when you vote the the badge allocation takes a little time to reflect

Can somebody help me understand, how Redis is used?