Choose SSR over SSG when:
- Content is per-user — a dashboard, cart, or profile page. SSG can't encode user-specific data at build time.
- Data changes very frequently — live scores, stock prices, breaking news. ISR revalidation windows would always show stale content.
- SEO matters AND content is real-time — SSR delivers fresh HTML to crawlers without client-side rendering delay.
- You need request-time context — cookies, headers, geolocation, A/B test assignments available only at request time.
Trade-offs of choosing SSR:
- Higher server cost — every request spins up rendering work.
- Higher TTFB vs CDN-cached static files.
- Must manage server scaling and cold starts.
💡 A common pattern: SSG the marketing/blog pages, SSR the dashboard, and CSR the deeply interactive editor.