Tier 2 needs to be fully interactive. If someone clicks on a menu after Tier 2 code loads and renders, they get immediate feedback about the interaction, even if the contents of the menu are not ready to render.
Tier 2 needs to be fully interactive. If someone clicks on a menu after Tier 2 code loads and renders, they get immediate feedback about the interaction, even if the contents of the menu are not ready to render.

Tier 3 includes everything that is only needed after display that doesn’t affect the current pixels on the screen, including logging code and subscriptions for live-updating data.