There is just a single path, why the concept of area is being is used here. I think that particular component should be renamed as Route Calculator Service.
Course: Grokking Modern System Design Interview for Engineers & Managers - Learn Interactively
Lesson: https://www.educative.io/courses/grokking-modern-system-design-interview-for-engineers-managers/design-of-google-maps
Thanks for bringing it up.
Firstly, I would like to clarify that the shortest path may not be unique; there can be more than one shortest path. For example, if distance is our shortest path criterion, there can be multiple paths with the same distance.
Secondly, the component is named “Area search service” because it helps find the subgraph of the area spanning the source and destination points. This allows the shortest path search to run only on that area’s graph rather than on the entire large road network graph of the world, making the path search more efficient and scalable. To make this point clear, we have updated the text defining the "Area search service”.