Server-Side Rendering Performance

SSR vs CSR.

Overview

Rendering strategy is the choice between SSR, CSR, SSG, and ISR for each page in a web application. Framework matters less than picking the right strategy per page; SSR optimises first paint, CSR optimises interactivity, SSG ships pre-rendered HTML, and ISR blends static with periodic regeneration. The wrong default applied site-wide is the root cause of most modern frontend performance problems.

• SSR (server-side rendering). HTML built per request. Best TTFB and SEO; cost is server compute on every page view.
• CSR (client-side rendering). Minimal HTML shell, JavaScript builds the UI in the browser. Strong post-load interactivity; weaker first-paint and SEO.
• SSG (static site generation). HTML built at deploy time and served from a CDN. Fastest possible response; only works for content that does not vary per request.
• ISR (incremental static regeneration). Static pages that revalidate on a schedule or webhook. The hybrid that handles “mostly static, sometimes fresh”.

The approach

Three habits keep rendering strategy matched to reality: choose per page rather than per app, monitor TTFB and time-to-interactive separately, and document why each page picked what it picked.

• Per-page strategy. Different pages have different needs. The product page needs SSG; the dashboard needs CSR; the article needs ISR.
• Monitor TTFB plus TTI. Time-to-first-byte and time-to-interactive both matter. Optimising one without the other masks regressions.
• SSG for genuinely static, ISR for stale-tolerant. Marketing pages and blog posts; documentation that updates daily.
• Documented rationale per page. Per-page the why-this-strategy. New team members inherit the reasoning instead of guessing.

Why this compounds

Each correct rendering choice compounds across every page view for that page. The team’s frontend mental model deepens; new pages inherit the methodology instead of inventing one.

• User experience improves. Right strategy per page means each page is fast in the way that matters for it.
• SEO follows naturally. SSR and SSG produce HTML crawlers can index; CSR-only pages quietly miss search traffic.
• Server cost matched to page value. SSG and ISR shift work to build time and CDN; SSR cost stays scoped to pages that need it.
• Year-one investment, year-two habit. The first per-page audit is heavy lift. By year two, every new page ships with a rendering choice on day one.