Complex sentence: Such a task is enormous and may take significant amount of time, while on the atomic level (where "atom" is defined as a single loosely-coupled service that is self-contained), most services are reusable regardless of the application.
Split into simpler sentences: Such a task is enormous and may take significant amount of time. While, on the atomic level, where'atom' is defined as a single loosely coupled service that is self contained, most services are reusable regardless of the application.