The framework components attempt to follow the principle of pragmatic (KISS) design. Practically, it means that each component must follow the given rules:
The framework relies on the application server to run some of its services. PHP codebase is mostly centered around quick delivery of efficient business logic. The application server, Golang based, is focused on efficiently solving infrastructure tasks.
Spiral application server is a customized version of RoadRunner.
Read about the application lifecycle here.