Partial hydration
Hydrera bara interaktiva components, inte hela page. Reducera JS-bundle + CPU-cost vid load. Pioneerd av Marko (eBay, 2014), populariserat av Astro 2021 ("Islands Architecture") + Qwik 2022.
Skiljs från full hydration (React/Vue default): traditional SSR hydratar entire page-tree → även static-content kostar JS-parse + CPU-cycles. Partial: server renders all, only specific components ("islands") get JS shipped. Astro: explicit client:load, client:visible, client:idle-directives. Qwik tar konceptet vidare: "resumability" — no hydration alls, JS lazy-loaded per interaction. Modern: React Server Components är React:s svar på partial-hydration.