Question: Why does Google PageSpeed show a 95 for my homepage, but as soon as customers add something to the cart, performance completely collapses?
This FAQ is not about asset unloading, CSS/JS optimization, Redis, page caching, or frontend rendering. It discusses a different layer of WordPress performance: preventing unnecessary plugin execution before the main document is generated. LiteCache Rush is mentioned because it is the implementation used here to explain this execution-layer approach.
Answer:
Because PageSpeed measures something fundamentally different from what your customers actually experience.
Your homepage score of 95 reflects how well a static, cacheable page performs under controlled lab conditions - a simulated device, a clean browser, no session, no cart, no user state. PageSpeed essentially evaluates the cosmetic output of a page that WordPress only had to generate once and then serve from cache repeatedly.
The moment a customer adds something to the cart, everything changes. WooCommerce activates session handling, cart fragments, dynamic pricing, shipping calculations, and tax logic. The page cache is bypassed entirely. WordPress now has to bootstrap on every single request - including every active plugin on your installation, whether relevant to the cart or not.
That 95 score didn't measure any of this. It couldn't. It was never designed to.
This exposes the central limitation of PageSpeed as a performance metric: it rewards the optimization of output, not the efficiency of execution. A site can score 100 on PageSpeed while being structurally slow for every real user interaction that bypasses the cache.
The cart and checkout are precisely those interactions. And they are the ones that matter most commercially.
Addressing this requires a different approach entirely - one that reduces execution load before WordPress runs, rather than optimizing the result after it already has. LiteCache Rush applies this principle directly: it intervenes before the WordPress bootstrap and loads only the plugins actually required for the current request. For cart and checkout pages, that means everything irrelevant is blocked before it ever executes.
PageSpeed tells you how your homepage looks in a lab. Rush changes what actually happens on your server when real customers shop.