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How I built an Amazon FBA Fee Solver and Notion-Style Bio Studio with Next.js 15

#buildinpublic #nextjs #react #webdev

Over the past few weeks, I set out to build a lightweight ecosystem of high-performance web utilities focused on 100% in-browser client execution with sub-second page loads.

Today, I launched two major tools:

  1. Amazon FBA & Profit Calculator (2026) at CalcHub
  2. Notion-Style Link-in-Bio & Font Studio at SnapBio

🛠️ Key Technical Architecture:

  • Framework: Next.js 15 (App Router), React 19, Tailwind CSS
  • Edge Deployment: Cloudflare CDN & Vercel Edge Network
  • Dynamic Multi-Tenant Routing: Automated custom subdomain routing (e.g. bio.yourname.com) powered by Vercel Domains API.
  • Client-Side Unicode Engine: In-browser transformation across 15+ mathematical Unicode blocks for the Instagram Font Generator.
  • SEO & Structured Data: Comprehensive JSON-LD schema (SoftwareApplication, FAQPage, HowTo) and automated dynamic sitemap.xml.

💡 What I Learned from In-Browser Calculation:

By executing all fee algorithms (FBA size tiers, referral brackets, ACoS simulation) directly in the user's browser, the server compute cost remains practically $0/month, while providing instant zero-latency feedback as sliders and inputs move.

Would love to get feedback on the UI/UX and calculation logic!

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