Intent built using

FlutterActivity.withCachedEngine()
on

FlutterViewController
initialized by using

initWithEngine: nibName: bundle:
on

FlutterActivity.createDefaultIntent() on

FlutterViewController initWithProject: nibName: bundle:
on

Surface on

CAEAGLLayer or

CAMetalLayer
on

At this point, the Layer tree generated by your Flutter
program, per frame, is converted into
OpenGL (or Vulkan or Metal) GPU instructions.

Memory and latency

Showing a Flutter UI has a non-trivial latency cost.
This cost can be lessened by starting the Flutter engine
ahead of time.