Too Long; Didn't Read
Redis is an in-memory database with sub-millisecond latency. It stores the data in the memory and not in the slower disks. Unlike a relational database where the data is stored in slower hard disks, Redis stores it in RAM. Redis takes milliseconds to access data as opposed to many hundreds of milliseconds using traditional methods. It is not a replacement for your database. Instead, it is built on top of your traditional database. Using Redis to make your website 30-40% faster.