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Full-stack developer · Rajkot, Gujarat, India

Software that runs the business.

I build custom ERP systems, GST billing software, SaaS platforms, vendor API integrations and fast, SEO-first websites.

I'm Swapnil Kotadiya. I design and engineer billing, ERP and SaaS platforms in ASP.NET Core, React and TypeScript, from offline desktop apps to multi-vendor sync engines.

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10
Case studies
3
Live websites
.NET · React
Core stack, with Node, MongoDB and SQL

Selected work

6 builds, end to end.

  1. 01 · Billing software

    Grevity

    Offline GST billing and inventory software for Indian businesses that runs entirely off a USB pendrive.

    Challenge

    Indian manufacturers and traders needed GST billing that works with no internet and no server.

    What I built

    I built Grevity, an ASP.NET Core (.NET 10) app with multi-company tenancy, GST invoicing that moves from Draft to Quotation to Order to Invoice, bill-of-materials production, live stock, party ledgers, payments, reports with Excel export and full audit logging.

    • ASP.NET Core
    • C#
    • Entity Framework
    • SQLite
    • Tailwind CSS
    Read case study: Grevity
    Grevity dashboard showing revenue, outstanding amount, a cash flow chart, receivables by age and recent invoices

  2. 02 · SaaS platform

    InFlow

    One platform for attendance, projects, client billing and payroll, built on ASP.NET Core, React and MongoDB.

    Challenge

    Teams were juggling attendance, projects, client billing and payroll across separate tools.

    What I built

    I built InFlow, one platform for the whole cycle. It covers clock-in and time logs, projects with Kanban boards, sprints and Git commit sync, client quotes, SoWs and invoices, payroll, leave approvals, announcements and real-time project chat.

    • ASP.NET Core
    • React
    • MongoDB
    • SignalR
    • Material UI
    Read case study: InFlow
    InFlow admin dashboard with project and task totals, a projects-by-status chart and upcoming deadlines

  3. 03 · Vendor integration

    Timeshare platform

    A platform that automates vacation-club inventory tracking across five vendor portals for a US travel company.

    Challenge

    A US travel company rented vacation-club inventory but tracked availability by hand across five vendor portals.

    What I built

    I built and maintain the platform that automates it, with integrations for Wyndham, Marriott, Hilton, BlueGreen and Capital Vacations using OAuth2 auth chains, Selenium login with cookie caching and a Chrome extension.

    • ASP.NET Core
    • C#
    • MongoDB
    • API Integration
    • Selenium
    Read case study: Timeshare platform
    Architecture diagram of vendor sources flowing through a sync engine into listing outputs

  4. 04 · Internal tool

    Grevity CMS

    A TypeScript admin CMS for plans, clients, subscriptions and signed pendrive-bound licence files.

    Challenge

    Grevity ships on hardware-locked pendrives, so the business needed one place to manage plans, clients, subscriptions and licence files.

    What I built

    I built a TypeScript monorepo admin CMS with a NestJS + Fastify API using Drizzle ORM on PostgreSQL (Supabase) and a React + Vite + Tailwind UI.

    • NestJS
    • React
    • TypeScript
    • PostgreSQL
    • Tailwind CSS
    Read case study: Grevity CMS
    Grevity CMS dashboard with totals for plans, clients and subscriptions and recent activity lists

  5. 05 · Agency website

    Infinitix

    A one-page React site where the infinity mark from the logo drives the hero, the sections and the motion.

    Challenge

    An IT agency needed a site that felt as engineered as its work.

    What I built

    I designed and built a one-page React + TypeScript site where the infinity mark from the logo is the structural device. One parametric curve draws the hero, becomes the thread between sections, drives the 6-stage process loop and orbits the tech stack.

    • React
    • TypeScript
    • GSAP
    • Tailwind CSS
    • Web Design
    Read case study: Infinitix
    Infinitix website hero with the headline Design. Engineer. Evolve. and an infinity curve

  6. 06 · Industrial website

    Stingray

    A framework-free site for an earthing-equipment manufacturer, with a scroll-driven scene that explains the product.

    Challenge

    An earthing-equipment manufacturer in Rajkot needed a premium site that explains what its products actually do.

    What I built

    I designed and built it framework-free in Vite + TypeScript, with a scroll-driven science scene where a canvas renderer shows fault current flowing from the electrode into the soil.

    • TypeScript
    • GSAP
    • Vite
    • Python
    • Responsive Design
    Read case study: Stingray
    Stingray Earthing website hero with the headline We Deal Economic Engineering and an earthing electrode scene

All projects

Every case study, filterable.

Services

Custom ERP, billing and SaaS development.

I work as a full-stack developer from Rajkot, India, with ASP.NET Core and React at the core. These are the kinds of projects I take on.

Tech stack across these projects

  • React
  • Tailwind CSS
  • ASP.NET Core
  • SQLite
  • TypeScript
  • C#
  • GSAP
  • JavaScript
  • MongoDB
  • Python
  • Responsive Design
  • Web Design
  • API Integration
  • Chart.js
  • CSS 3
  • Entity Framework
  • Express
  • FastAPI
  • HTML5
  • Material UI
  • NestJS
  • Node.js
  • PDF.js
  • PostgreSQL
  • PWA
  • Selenium
  • SignalR
  • Vite
  • WebView2

FAQ

Questions clients ask.

What kind of software do you build?

Mostly business software: GST billing and inventory, employee and payroll platforms, licensing systems, vendor integrations and marketing websites. The case studies on this site show each one.

Which technologies do you work with?

ASP.NET Core and C#, React and TypeScript, Node.js and NestJS, with MongoDB, PostgreSQL and SQLite. For websites I use TypeScript with GSAP.

How do we start a project?

Send a message through the contact page or hire me on Upwork. Tell me what the software needs to do and who will use it, and I will reply with questions and a proposed approach.

Do you work on existing codebases?

Yes. One of the case studies here is a platform I built and continue to maintain for a client, adding vendor integrations over time.

Have software that needs building?

Tell me what it needs to do. I reply by email with questions and a proposed approach.

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