Related: I do believe starting off at the "second" level of abstraction (as opposed to implementing the direct surface area of the service) is not premature as

Related: I do believe starting off at the "second" level of abstraction (as opposed to implementing the direct surface area of the service) is not premature as it helps to better understand the problem space, and on the implementation side, as soon as you identify the building blocks, the rest would be really just boilerplate. if you got time, rinse and repeat.