Performance Patterns in Astro

Astro's "Islands Architecture" is a game changer because it defaults to zero JavaScript. This is the opposite of the Single Page Application (SPA) hydration model.

Partial Hydration

Instead of hydrating the entire page (re-running all JS to attach event listeners), Astro allows you to wake up just the interactive bits.

• The header is static? No JS.
• The blog content is static? No JS.
• The generic "Buy Now" button? Hydrate on visible.

The Result

We saw a 40% reduction in TTI (Time to Interactive) simply by switching to Astro for our marketing pages. It forces you to be intentional about what scripts you send to the user.