Automated VAT reconciliation
Accountants previously reconciled VAT manually. They now paste tables copied from Mexico’s SAT portal; the tool cleans and structures the data, then reconciles it against company records in under a minute.
Case study · Enterprise operations
PASSA Operations Platform
I consolidated five separate desktop applications into one secure, responsive web platform for accounting, production, inventory, sales, and administration.
Internally named Next: the next step from disconnected tools toward one shared operational system.
- Company
- PASSA Agroservicios
- Role
- Product design, architecture, frontend, backend, infrastructure, and maintenance
- Timeline
- August 2021—Present
- Core stack
- TypeScript · React · Next.js · Python · Flask · SQL Server · Docker · Nginx
5legacy desktop applications consolidated
~100employees using the platform
30branches connected
50+reports, tools, and catalogs
01 / Context
From fragmented legacy tools to one operational platform.
PASSA relied on five desktop applications built over more than two decades. Access depended on installed computers, interfaces contained obsolete options, and employees still completed important workflows manually.
I led the platform end to end: product and interface design, architecture, technology selection, frontend and backend development, containerization, Nginx configuration, deployment, and ongoing maintenance. The existing SQL Server database remained in place; I extended it with permission tables and stored procedures required by the new workflows.
The result is a responsive system that preserves valuable business data while replacing outdated workflows with clearer catalogs, decision-support reports, and purpose-built operational tools.
02 / Business impact
Software tied to measurable operational results.
Inventory recovered through production planning
When an item appeared unavailable for an order, the planning tool identified more than MXN $400,000 of stock in a warehouse. A targeted second search located a two-year-old lot that the team had not found manually.
03 / Architecture
A pragmatic modernization layer around trusted business data.
The platform runs on an internal company server. I designed the web application and its deployment around the existing SQL Server data and an established high-performance query service.
01Responsive clientReact · Next.js · TypeScript
02Application backendPython · Flask · validation and authorization
03Query serviceExisting C++ API adapted for project needs
04Business dataSQL Server · stored procedures · daily backups
Docker containers package the application and Nginx handles internal traffic. I integrated, adapted, and help maintain the externally developed C++ query API; its optimized SQL execution made it a practical fit for the existing environment.
04 / Permissions and reliability
Authorization enforced at every meaningful boundary.
The most demanding part of the platform was designing permissions that stay understandable for users while remaining enforceable across navigation, routes, and write operations.
- Permission-driven navigation
A three-level menu—menus, submenus, and screens—is generated from each user’s authorized routes.
- Route protection
Next.js middleware checks the session token and screen permission whenever a protected route is opened.
- Backend enforcement
The backend repeats authorization checks, including separate write permissions for catalog changes.
- Immediate revocation
Permission updates alter navigation immediately; blocked users have all sessions closed and cannot bypass access by entering a URL manually.
- Layered validation
Zod validates client input, backend and stored-procedure rules protect data integrity, and focused toast messages make failures easier to diagnose.
Automated test.ts files run against a local database so behavior can be verified without using production data. SQL Server backups are managed daily by the existing infrastructure.
05 / Product evidence
Interfaces designed for real accounting and operational work.
The screenshots below use anonymized production data. They show the range of workflows supported by the same design system and permission model.
06 / Responsive access
The same permission model, available beyond installed desktops.
On smaller screens, the navigation collapses into a menu while preserving the same hierarchy and user-specific permissions. This lets authorized employees consult catalogs and reports from phones or tablets across branches.
07 / Takeaway
Modernization works when technical choices serve the operation.
This project strengthened my ability to own a long-lived product rather than only deliver isolated screens. The most valuable work has been understanding how accounting, production, inventory, and sales connect—and turning those relationships into software employees can trust every day.