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

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 Astro 5 Fastify + React Winner
TTFB (p50) 50.5ms 42.95ms ▶
TTFB (p95) 52.23ms 46.06ms ▶
LCP (p50) 80ms 70ms ▶
LCP (p95) 86.2ms 78.2ms ▶
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 99 =
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 3580ms ▶
Exploration Tokens 2756 3244 ◀
Files Examined 8 10 ◀
Validation Accuracy 86% 80% ◀
Time Per File 494ms 358ms ▶
Tokens Per File 3496 3060 ▶
Efficiency Score 33.49 27.95 ◀

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 1869ms ▶
Exploration Tokens 2764 3278 ◀
Files Examined 8 10 ◀
Validation Accuracy 81% 68% ◀
Time Per File 280ms 187ms ▶
Tokens Per File 3474 3061 ▶
Efficiency Score 49.18 26.22 ◀

Build Metrics

Metric Astro 5 Fastify + React Winner
Bundle Size (JS) 242.7KB 283.6KB ◀
Bundle Size (CSS) 22.6KB 23.1KB ◀
Build Time 0s 0s =
Dependencies 18 21 ◀

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