Evolving Patterns
The above is a somewhat arbitrary breakdown of different approaches based on a snapshot in time. Design patterns are still evolving. Recently, model server designs have started to adopt more of the technologies of general service infrastructure such as Docker containers and kubernetes, so many model servers have started to share properties of the model microservice design discussed above. For a deeper dive into the general concepts of model server designs, you can check out my book on machine learning systems.
Serving PyTorch Models
So, if you're a PyTorch user, what should you use if you want to take your models to production?
If you're on mobile or working on an embedded system like a robot, direct embedding in your application is often the right choice. 
For mobile specifically, your use case might be served by the ONNX export functionality.