Next.js 16 vs Fastify + React
Real-world performance comparison based on identical SaaS dashboard implementations.
Performance Metrics
Lower is better for all metrics. Green indicates the faster framework.
| Metric | Next.js 16 | Fastify + React | Winner |
|---|---|---|---|
| TTFB (p50) | 120.95ms | 340.9ms | ◀ |
| TTFB (p95) | 121.63ms | 402.72ms | ◀ |
| LCP (p50) | 148ms | 370ms | ◀ |
| LCP (p95) | 156ms | 430.6ms | ◀ |
| 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 | 91 | 96 | ▶ |
| 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 | N/A | N/A | - |
| Exploration Tokens | N/A | N/A | - |
| Files Examined | N/A | N/A | - |
| Validation Accuracy | N/A | N/A | - |
| Time Per File | N/A | N/A | - |
| Tokens Per File | N/A | N/A | - |
| Efficiency Score | N/A | N/A | - |
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 | N/A | N/A | - |
| Exploration Tokens | N/A | N/A | - |
| Files Examined | N/A | N/A | - |
| Validation Accuracy | N/A | N/A | - |
| Time Per File | N/A | N/A | - |
| Tokens Per File | N/A | N/A | - |
| Efficiency Score | N/A | N/A | - |
Build Metrics
| Metric | Next.js 16 | Fastify + React | Winner |
|---|---|---|---|
| Bundle Size (JS) | 2408.8KB | 285.3KB | ▶ |
| Bundle Size (CSS) | 23.4KB | 23.1KB | ▶ |
| Build Time | 7.1s | 2.5s | ▶ |
| Dependencies | 18 | 21 | ◀ |
Want to see more framework comparisons?
View All Comparisons