We will go through what a modern REST API is, see what the least features we should provide to the clients are, how we can test it super fast (because testing APIs can be very time consuming!), and how we can optimize it’s performance. The talk will not be bound to any specific API spec (JSONAPI, Serien, HAL etc) but will go though all the principles of a modern REST API. However we will challenge Roy Fieldings’s thesis on REST APIs (is it still valid? we will see!) along with current specs which are based on Roy’s thesis (like JSONAPI spec) especially when high performance part of the API design.