Final Thoughts
Hydration is SSR's destiny. The moment the server sends HTML, you need a process to bring that HTML to life. I initially thought "React handles it automatically," but in reality, there's a lot to consider: the gap between FCP and TTI, hydration mismatch errors, JavaScript bundle size, user experience.
React 18's Selective Hydration and Streaming SSR attempt to narrow this gap. Astro's Islands Architecture minimizes hydration altogether. Next.js's React Server Components fundamentally avoid the problem by creating components that don't need hydration.
Ultimately there's no single answer. Depending on your project's characteristics, if you need SSR, optimize hydration. If you have lots of static content, consider Islands Architecture. If you have complex interactions, CSR might be better. What matters is understanding "why ghost buttons appear." Only then can you improve user experience.