INOVIT Dealer Portal

A B2B e-commerce platform replacing a legacy .NET ERP — without ever taking it offline.

The new Django API and the old .NET system read and write the same SQL Server tables, in parallel, processing live dealer orders. 49 API endpoints, four regional databases behind one codebase, cross-repo OpenAPI type generation, and a migration that changed not a single column of the production schema.

Stack: React 19
TypeScript
Django 5
DRF
SQL Server
Ant Design 6
Vite 8
Docker
AWS
Category: Full-stack

My Role

Solo · greenfield rewrite

What I owned

Everything. Architecture design, frontend, backend, database mapping, CI/CD pipelines, Docker infrastructure, monitoring, and production deployment. Solo developer on a greenfield rewrite.

The hard part

The legacy .NET ERP processes live orders daily — it could not go offline, and its database schema could not change. I had to build a new system that reads and writes the same tables simultaneously, without the old system ever noticing.

At a Glance

By the numbers

Downtime: 0
Schema Changes: 0
API Endpoints: 49
Regions: 4
ORM Models: 44
Developer: 1

Tech Stack

Five layers

Frontend: React
TypeScript
Vite
Ant Design
Backend: Django
DRF
Python
Gunicorn
Database: SQL Server
mssql-django
4 regional databases · 42 unmanaged models
Infra: AWS Lightsail
Docker
Caddy
GitHub Actions
S3
Lambda
SES
Testing: Vitest
Playwright
pytest
OpenAPI drift checks in CI

Two Systems, One Database

Parallel operation

Django maps 42 legacy tables with managed = False: the ORM works normally and never migrates them. Both systems process live orders in parallel, unaware of each other.

New System

React SPAAnt Design · lazy routes

CaddyTLS · reverse proxy

Django APIGunicorn · JWT · region routing

Legacy

.NET 4.8 ERPStill running · still processing orders

Alongside

S3 + CDNDual-bucket · WebP via Lambda

MonitoringUptime Kuma · Dozzle · Beszel

SQL Server 2025AU · UK · US · Demo — both systems read/write

One Codebase, Four Databases

Region routing

A dealer never picks a region: the token carries it, and one Django instance routes every ORM query to the right database.

Dealer logs inJWT carries region claim

MiddlewareExtracts region per request

DB RouterRoutes ORM to the correct database

Isolated data per region AUUKUSDemo

Trade-offs

Decisions that held

OpenAPI as the contract boundary

Three repos, one developer — the frontend had to break loudly when the backend API changed. Backend CI generates the OpenAPI spec, dispatches it to the frontend repo, and auto-generates TypeScript types. Contract drift is a build failure, not a silent runtime bug discovered by a dealer.

Auth caching across AWS instances

The SQL Server lives on a separate AWS instance. Every auth lookup crosses the network. A 5-minute LocMemCache on the API server eliminates that round-trip for repeat requests — short enough that ERP-side user changes (disabling an account, changing permissions) still propagate within minutes.

2 MB bundle budget

A hard CI gate at 2 MB catches size regressions before they merge — keeps the app fast without relying on manual review to spot bloated imports.

Build-time architecture enforcement

Nine feature modules can turn into a dependency web fast. ESLint rules encode the dependency direction (types → services → hooks → features) and forbid cross-feature imports. Architectural violations fail the build — they don't survive as "we'll fix it later" TODOs.

Live site

Want the full walkthrough?

Happy to talk through the architecture, the decisions, and the trade-offs behind this build.

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