How does React 18 streaming SSR differ from traditional SSR, and how do you decide which content to stream vs block on — including the impact on FCP and TTFB?

Imagine you're building a sandcastle. Traditional SSR is like waiting for the whole castle to be built before you can play. Streaming SSR is like getting a bucket of sand first to start playing while the rest comes. Suspense boundaries let you decide which parts are ready early and which need more time.