Myth: SPAs feel faster after the first load

Myth: SPAs feel faster after the first load
Client-side route change: 'instant' paint, but INP p75 = 290ms and LCP recorded per soft-nav.
SPAs swap views without a full reload, which feels fast. But each soft navigation re-runs JS-driven rendering on the main thread, and CWV now measures soft navs.
— A 320KB hydration pass on route change blocks input for ~270ms; the user taps a link and waits.
— Server-rendering the next view as HTML beat client routing: interaction-ready 270ms -> 60ms.
Felt-speed isn't measured-speed once you log per-interaction.
Takeaway: soft-nav INP 290ms hid behind 'instant' SPA paint.

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