Astro 5 vs Fastify + React

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

Astro 5

Astro 5

VPS

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The web framework for content-driven websites. Astro's revolutionary Islands architecture ships zero JavaScript by default—interactive components hydrate independently only where needed, dramatically reducing bundle sizes. Astro 5 introduces Content Layer for type-safe content collections, Server Islands for mixing static and dynamic content, and improved build performance. The framework is UI-agnostic: use React, Vue, Svelte, Solid, or vanilla JS components in the same project. Perfect for marketing sites, documentation, blogs, and any content-heavy application where performance matters. Astro consistently achieves perfect Lighthouse scores with minimal effort.

Fastify + React

Fastify + React

Render

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Performance Metrics

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

Metric Astro 5 Fastify + React Winner
TTFB (p50) 50.5ms 227.7ms ◀
TTFB (p95) 52.23ms 484.46ms ◀
LCP (p50) 80ms 360ms ◀
LCP (p95) 86.2ms 945.6ms ◀
CLS 0 0 =
TBT 0 ms 0 ms =
LCP → TTFB 214 ms N/A -
LCP → Load Delay 0 ms N/A -
LCP → Load Duration 0 ms N/A -
LCP → Render Delay 535 ms N/A -
Performance Score 99 98 ◀
SEO Score 92 92 =
Accessibility Score 79 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 Astro 5 Fastify + React Winner
Exploration Time 3955ms N/A -
Exploration Tokens 2756 N/A -
Files Examined 8 N/A -
Validation Accuracy 86% N/A -
Time Per File 494ms N/A -
Tokens Per File 3496 N/A -
Efficiency Score 33.49 N/A -

LLM Understanding (Claude Haiku 4.5)

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

Metric Astro 5 Fastify + React Winner
Exploration Time 2240ms N/A -
Exploration Tokens 2764 N/A -
Files Examined 8 N/A -
Validation Accuracy 81% N/A -
Time Per File 280ms N/A -
Tokens Per File 3474 N/A -
Efficiency Score 49.18 N/A -

Build Metrics

Metric Astro 5 Fastify + React Winner
Bundle Size (JS) 242.7KB 285.3KB ◀
Bundle Size (CSS) 22.6KB 23.1KB ◀
Build Time 0s 2.5s ◀
Dependencies 18 21 ◀

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