A developer built InvoiceDesk, a production-ready invoicing app for Indian businesses, using Next.js, MongoDB, and Zustand. The tool handles complex GST compliance—automatically calculating CGST, SGST, or IGST based on GSTINs—and generates pixel-perfect PDFs. It focuses on solving real-world pain points like data retention and performance for SMBs.

The project tackled common scaling issues by splitting a monolithic Zustand store into domain-specific stores, eliminating cascade re-renders. To stay within MongoDB Atlas's free tier, a strict data retention policy archives or deletes old records. Security uses dual-token JWT with HTTP-only cookies and multi-tenant isolation from the start.

For PDF generation, the author moved from Puppeteer to html2canvas + jsPDF for consistency between the live UI and exported files. The open-source app is available on GitHub, offering a five-minute setup with a demo login. It serves as a practical template for developers building financial tools that require strict compliance and high performance.