Next.js 16 vs Fastify + React

Real-world performance comparison based on identical SaaS dashboard implementations.

Next.js 16

Next.js 16

Vercel

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Next.js deployed on its native platform—the way it was designed to run. Vercel's infrastructure is purpose-built for Next.js, providing automatic edge caching, instant rollbacks, and preview deployments for every git push. ISR (Incremental Static Regeneration) works seamlessly on Vercel with on-demand revalidation APIs and automatic cache invalidation across their global edge network. Edge Functions run your middleware in 30+ regions with sub-millisecond cold starts. This deployment demonstrates Next.js at its most optimized, with Vercel handling image optimization, analytics, and Web Vitals monitoring automatically.

Fastify + React

Fastify + React

VPS

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Node.js high-performance web framework combined with React SSR. Fastify is one of the fastest Node.js frameworks, built on a robust plugin architecture with JSON Schema validation and automatic OpenAPI documentation. This implementation uses Fastify as the server with custom React SSR integration. Fastify's encapsulation model keeps plugins isolated, while hooks provide fine-grained request lifecycle control. Ideal for teams with existing Node.js/Express experience who want better performance and structure. Fastify's plugin ecosystem covers everything from rate limiting to WebSocket support.

Performance Metrics

Lower is better for all metrics. Green indicates the faster framework.

Metric Next.js 16 Fastify + React Winner
TTFB (p50) 44.7ms 42.95ms ▶
TTFB (p95) 44.86ms 46.06ms ◀
LCP (p50) 62ms 70ms ◀
LCP (p95) 70.2ms 78.2ms ◀
CLS 0 0 =
TBT 0 ms 0 ms =
LCP → TTFB N/A N/A -
LCP → Load Delay N/A N/A -
LCP → Load Duration N/A N/A -
LCP → Render Delay N/A N/A -
Performance Score 96 99 ▶
SEO Score 100 92 ◀
Accessibility Score 88 80 ◀
Best Practices Score 100 100 =

LLM Understanding (Claude Opus 4.5)

How efficiently Claude Opus 4.5 understands the codebase. Based on exploration + validation tests.

Metric Next.js 16 Fastify + React Winner
Exploration Time 3883ms 3580ms ▶
Exploration Tokens 3963 3244 ▶
Files Examined 11 10 ▶
Validation Accuracy 100% 80% ◀
Time Per File 353ms 358ms ◀
Tokens Per File 3245 3060 ▶
Efficiency Score 43.28 27.95 ◀

LLM Understanding (Claude Haiku 4.5)

How efficiently Claude Haiku 4.5 understands the codebase. Based on exploration + validation tests.

Metric Next.js 16 Fastify + React Winner
Exploration Time 3029ms 1869ms ▶
Exploration Tokens 3991 3278 ▶
Files Examined 11 10 ▶
Validation Accuracy 99% 68% ◀
Time Per File 275ms 187ms ▶
Tokens Per File 3225 3061 ▶
Efficiency Score 55.84 26.22 ◀

Build Metrics

Metric Next.js 16 Fastify + React Winner
Bundle Size (JS) 613.3KB 283.6KB ▶
Bundle Size (CSS) 23.3KB 23.1KB ▶
Build Time 0s 0s =
Dependencies 18 21 ◀

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