TanStack Start vs Fastify + React

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

TanStack Start

TanStack Start

VPS

View Live Demo

A full-stack React framework from the creators of TanStack Query, Table, and Router. Built on Vinxi (a Vite-based meta-framework engine), TanStack Start brings the TanStack philosophy of type-safety and developer experience to server rendering. Features isomorphic data fetching with TanStack Router's loader patterns, full-stack type safety from database to component, and first-class support for server functions. The router provides file-based routing with powerful search param management. Still in beta but rapidly maturing, TanStack Start appeals to developers who love TanStack Query's patterns and want them extended to the full stack.

Fastify + React

Fastify + React

VPS

View Live Demo

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 TanStack Start Fastify + React Winner
TTFB (p50) 50ms 42.95ms ▶
TTFB (p95) 55.06ms 46.06ms ▶
LCP (p50) 76ms 70ms ▶
LCP (p95) 84ms 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 99 99 =
SEO Score 92 92 =
Accessibility Score 86 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 TanStack Start Fastify + React Winner
Exploration Time 3649ms 3580ms ▶
Exploration Tokens 3993 3244 ▶
Files Examined 10 10 =
Validation Accuracy 93% 80% ◀
Time Per File 365ms 358ms ▶
Tokens Per File 3258 3060 ▶
Efficiency Score 31.16 27.95 ◀

LLM Understanding (Claude Haiku 4.5)

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

Metric TanStack Start Fastify + React Winner
Exploration Time 3047ms 1869ms ▶
Exploration Tokens 4017 3278 ▶
Files Examined 10 10 =
Validation Accuracy 80% 68% ◀
Time Per File 305ms 187ms ▶
Tokens Per File 3263 3061 ▶
Efficiency Score 30.79 26.22 ◀

Build Metrics

Metric TanStack Start Fastify + React Winner
Bundle Size (JS) 382.4KB 283.6KB ▶
Bundle Size (CSS) 22.8KB 23.1KB ◀
Build Time 0s 0s =
Dependencies 21 21 =

Want to see more framework comparisons?

View All Comparisons