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A complete SME information system, built single-handedly

13 interconnected apps: sales, workshop, rentals, invoicing and e-commerce

Key figures

applications and services
13
lines of code
250,000+
automated tests
1,800+
commits
1,600+

Context

A distribution and services SME was running on spreadsheets, e-mails and disconnected tools. Sales, workshop, rentals, invoicing, stock and online sales had to be unified.

My role

From design to operations, fully autonomously.

Solution

I designed and built 13 interconnected applications and services. At the core sit a single business API and an e-commerce platform connected to a custom ERP with an integrated point of sale.

Around them, six business applications cover the workshop, field operations, installation, rentals, bank reconciliation and robot sales. A shared SSO and a common design system unify access and interfaces. Everything runs on 2 monitored production servers.

Key features

  • One central business API

    A single backend serves the internal applications, the showcase website and the online store.

  • E-commerce connected to the ERP

    API, storefront and back-office, with the ERP as the single source of truth for the catalogue.

  • A custom ERP with a connected POS

    Stock, inventory, e-invoicing and in-store payments.

  • One identity for 9 applications

    SSO with MFA replaces shared accounts and centralises access revocation.

Engineering challenges

  1. 1

    From monorepo to dedicated repositories

    The initial monorepo was split, in a controlled way, into dedicated repositories.

  2. 2

    Gradual migration to Next.js 16

    Legacy Create React App frontends are moving to Next.js 16 and the published design system.

  3. 3

    Consistent tooling

    A single package manager, pnpm, across every repository.

  4. 4

    Coordinated, reversible SSO cutover

    The API and 7 frontends moved to SSO in a single cutover, designed so it could be rolled back.

Tech stack

Frontend
Next.js 15/16React 19TypeScriptTailwindshadcnnext-intl
Backend
Node.jsExpressMedusaJS 2PrismaZodPHP 8Dolibarr 22
Data
PostgreSQL 16Redis 7MeiliSearchIndexedDB
Security
ZitadelOIDC/PKCEBFF
Infrastructure
DockerGitHub ActionsGHCRNginxCloudflare TunnelTailscalePrometheusGrafanaLokiAlertmanagerBorg
Integrations
MollieResend
Quality
Vitest

Ecosystem overview

Application ecosystem diagramPublic websites and business applications rely on the central API and the e-commerce platform, which connect to the ERP, the SSO identity provider and observability.

Public websites & business apps

  • SEO showcase website
  • Store & back office
  • Workshop & field
  • Equipment rental
  • Sales & installation
  • Bank reconciliation
  • Shared design system

Application core

  • Central business API
  • E-commerce platform

ERP, identity & operations

  • ERP & connected point of sale
  • Catalog imports
  • SSO & MFA
  • Infrastructure & observability

A project of this scale?

Let's talk about your context: I'll tell you frankly what is feasible, and how long it takes.

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