KISS is stands for “Keep It Simple, Stupid”. This principle says about to make your code or system simple. You should avoid unnecessary complexity. A simple code it’s easier to maintain and easier to understand.

You can apply this principle in the design and in the implementation of the code. You should eliminate duplicated code, should remove unnecessary features, use names for APIs and methods that makes sense and matches their responsibilities.

You also should separate the responsibilities of your applications and the responsibilities from the layers of the systems. Most systems work best if they are kept simple rather than making them complex designs; Therefore, simplicity should be a key goal in design and unnecessary complexity should be avoided.

https://medium.com/design-microservices-architecture-with-patterns/software-architecture-design-principles-kiss-yagni-dry-341ce969212c