---
title: "Fullstack Development - José DA COSTA"
description: "Fullstack development, the way I see it, is the **language polyglossia required to ship a production SaaS**: backend, frontend, scripting, and the ability to pick the right tool for each layer. I cove"
locale: "en"
canonical: "https://portfolio.josedacosta.info/en/skills/fullstack-development"
source: "https://portfolio.josedacosta.info/en/skills/fullstack-development.md"
html_source: "https://portfolio.josedacosta.info/en/skills/fullstack-development"
author: "José DA COSTA"
type: "skill"
slug: "fullstack-development"
generated_at: "2026-04-26T21:12:18.350Z"
---

# Fullstack Development

Icon: ⚙️

## My definition

Fullstack development, the way I see it, is the **language polyglossia required to ship a production SaaS**: backend, frontend, scripting, and the ability to pick the right tool for each layer. I cover the **PHP** chain (Joomla, Zend, Symfony 2-7, Magento 1-2), the **JVM** (Java SE, Spring, Hibernate, Kotlin Android), and the **modern TypeScript** ecosystem (Node, Next.js 16, React 19, Prisma 7, Drizzle, Bun). It is the polyglot profile that lets a CTO step into the team's code. not to rewrite for them, but to defend code reviews, absorb load spikes, and arbitrate senior technical choices.

### Context

My current rhythm mixes **daily code** (ACCENSEO product lines, **234K solo lines** on the accounting SaaS, OSS packages like tailwindcss-obfuscator) and **monthly review** (pair-programming with the apprentices, senior reviews on customer codebases). 31 technical references + 15 mobile in the portfolio (Top 3 frequency). Polyglossia is not an aesthetic goal: it is the consequence of **18 years** of successive roles each carrying their own stack. Joomla 1.5 at ABDC, Zend Framework at Pluxnet, Magento 1.10 at Smile, Symfony 3-5 at Pichet, Next.js 16 at ACCENSEO.

### Relevance

The big 2026 shift is that **the cost of writing code dropped with AI, not the cost of reading it**. Stack Overflow analyses it in [Why demand for code is infinite: How AI creates more developer jobs](https://stackoverflow.blog/2026/02/09/why-demand-for-code-is-infinite-how-ai-creates-more-developer-jobs/): with **80%+ adoption** of AI coding tools among professional developers and roughly **51%** daily use, the agent layer churns code at scale. but **critical reading, system design, and architecture review** have become the differentiator. The CTO who reviews a TypeScript + Prisma + Drizzle codebase in pair-programming with Claude Code ships faster than the one who delegates.

## My evidence

### Shipping 234K lines solo on the ACCENSEO accounting SaaS

**Context:** On the ACCENSEO accounting SaaS in 2025-2026, I was the only human developer facing a product no early-stage team usually ships alone: French accounting, taxation, banking (Open Banking PSD2), invoicing, 2026-2027 e-invoicing compliance, AI assistant. The cadence was unforgiving: if I dropped below **8K lines a month for 14 months**, the product would not be ready before the e-invoicing deadline.

**Action:** I ran a complete full-stack cycle every day: **Next.js 16 + React 19 + TypeScript** on the UI side, **Prisma + PostgreSQL** on the data side, **Better Auth** with MFA (email, TOTP, SMS), **AI SDK** for multi-provider orchestration (OpenAI, Claude, Gemini), **Stripe** for SaaS subscriptions, and a dedicated **Node.js microservice** for automated invoice retrieval. I personally handled the **Open Banking PSD2** integration across 3 providers in parallel (GoCardless/Nordigen, Bridge, Qonto), the **EDI Teledec** submissions for VAT / IS / CFE / DAS2 / PAS, and a **Chrome extension** for automated form-filling on impots.gouv.fr. The pair-programming with Claude Code carried 80-85% of the implementation, but every file was reviewed, every tax computation validated by script, every feature put through non-regression tests.

**Result:** **234K lines shipped solo**, **42 autonomous features**, **382 API routes**, **91 Prisma models**, **6 differentiated roles**, and the platform was running production-ready by the end of the cycle with 2026-2027 e-invoicing compliance reached ahead of the regulatory deadline.

**Value added:** What struck me on this project is that **staying an operator as CTO** changes everything: without the daily fullstack practice, I would never have framed a regulated domain in months. That posture - **a CTO who still codes** - is the one I want to keep on the next scale-up role, because it earns me the right to challenge senior technical decisions instead of delegating them.

### Publishing the OSS package tailwindcss-obfuscator

**Context:** Late 2025 I needed a Tailwind v4 obfuscation tool for several ACCENSEO engagements, and the only existing alternative was broken. Rather than crafting a workaround per customer, I decided to **turn it into an OSS product** - because a well-built npm package costs less to maintain than a dozen custom patches. The window was tight: **6 weeks** before the community fell back to hacks.

**Action:** I set up a **TurboRepo monorepo** with **pnpm workspaces** to drive **25 internal modules**, **5 bundler plugins** (Vite, Webpack, Rollup, esbuild, Nuxt module) sharing the same core engine, and a **Commander.js CLI** for framework-less usage. The stack: **TypeScript 5.7**, **Babel AST** to parse JSX/TSX/Vue/Svelte/Astro/Qwik, **PostCSS** to transform compiled CSS, **magic-string** to preserve sourcemaps, **Vitest** for the **295 unit and e2e tests**, and **VitePress** for the docs. Strict typing across the codebase, builds via **tsup** with full sourcemaps.

**Result:** **82K lines of TypeScript** published to npm in 6 weeks, **10 frameworks supported**, **automatic detection** of Tailwind v3 vs v4, **first Tailwind v4-compatible tool** on the market. Picked up by external teams within the first weeks, organic mentions in tech newsletters.

**Value added:** That package is what kept me **sharp on modern TypeScript outside customer time**. I have made it a rule to ship at least one OSS per year for the same reason: a CTO who stops publishing code eventually loses the daily reading reflex. And it is also a concrete credibility signal when I discuss a scale-up role - people ask for the OSS, not the resume.

### Full-stack Magento Enterprise refit at Fleurance Nature

**Context:** On the Fleurance Nature refit in 2017, I came in as **Senior Software Engineer full-stack** at Smile on a **Magento Enterprise Edition 1.10** platform: **60 accumulated custom modules**, **1,040 modified PHP files**, **3 stores** (Fleurance Nature France, International, Mincifine) to refit simultaneously. The complexity came from both backend (EAV pricing matrix, 4 customer groups, bidirectional ERP) and frontend (mobile responsive, 3 distinct themes, internationalisation).

**Action:** I owned **backend through frontend** without a hand-off: server-side **PHP 5.3 + Zend Framework + Magento EE 1.10**, **MySQL** with EAV, **Varnish** as reverse proxy, and the **ElasticSearch backport on Magento 1.10** nobody had done before (autocomplete, faceted navigation, virtual categories). Front-side I produced the **responsive wireframes** (mobile, tablet, desktop), wrote the **graphic specifications for the 3 themes**, integrated the **WordPress blog via RSS parsing** (512 articles migrated lossless), and shipped the responsive front-end theme on the 3 stores. I documented the **functional specs across 7 versions** (from 30 to 50 pages) as the business cases unfolded.

**Result:** Production rollout across **8 environments** with zero major regression, the **58-day post-launch warranty** handled in person, and the refitted platform held **for more than 5 years in production** without any further rewrite.

**Value added:** That assignment locked in a reflex I now replay: **legacy PHP depth + modern stacks** are not 2 separate worlds. Being able to read a Magento 1.x or Symfony 2 codebase today gives me access to CTO advisory audits that strictly modern-TypeScript profiles cannot run. It is exactly what let me chain Symfony 3-7 then the modern TypeScript stack with no breaks.

## My self-critique

### Mastery level

### My levels per stack

- **PHP** (Joomla, Zend, Symfony 2-7, Magento 1-2): Expert, 16 years
- **TypeScript / Node / Java** (Spring, Hibernate): Senior
- **Kotlin Android, Scala, Angular**: Confirmed

Polyglossia is not an aesthetic goal but a consequence of the project: each role brought its stack, I keep practising it as long as it serves. What still needs strengthening: **Bun + edge runtimes in production** and Kotlin Multiplatform for cross-mobile.

### Importance in my profile

Major differentiator versus CTOs who stopped coding. It is what gives me the right to challenge a senior technical decision, run a serious code review, and absorb a load spike. It is also what makes a solo-grade delivery cycle possible early-stage: the [ACCENSEO accounting SaaS](/en/achievements/plateforme-comptabilite-saas) would not have been framed and shipped without this polyglossia.

### Acquisition speed

Recent cadence indicator: **234K lines shipped solo** in 14 months on the accounting SaaS (2025-2026), and **6 weeks** to ship the first Tailwind v4-compatible obfuscator from scratch on Babel AST + PostCSS.

### Advice (for myself and others)

To myself: ship at least one OSS package per year to stay sharp outside the customer-comfort zone, never lose daily code reading even when the management load explodes. To others: *do not chase polyglossia for itself*, pick a language per project, execute it fully, capitalise on the patterns. Writing discipline (automated tests, strict typing) matters more than the novelty of the stack.

## My evolution in this skill

### Role in my professional project

Fullstack development is **what keeps my CTO scale-up posture credible on the engineering side**. In the 24-month plan, it lets me pair-program with my teams, arbitrate senior code reviews, ship an MVP solo on a new market, and reinforce team cadence through reverse mentoring. Without it, the role tilts to a purely managerial posture and loses its operational lever.

### Mid-term target level

The observable goal is to **ship a complete MVP solo (back + front + infra) in under 6 weeks** on a modern stack, and to **co-author a referenced OSS package** in the community. Practically: bring TypeScript / Node / Bun to Senior+, keep PHP at Expert, open Senior on Kotlin if mobile becomes relevant.

### Current training

Daily code on ACCENSEO products (accounting SaaS, OSS packages), weekly pair-programming with alternants, monthly third-party codebase reviews (consulting audits). Master in Software Engineering active until 2026.

### Future training

Possible **Kotlin Multiplatform** deep-dive if an ACCENSEO product requires cross-platform mobile. [Total TypeScript](https://www.totaltypescript.com/) (Matt Pocock) program planned 2026 to stabilize the Senior+ level. AWS Developer Associate certification considered 2027.

## Progression across journey

This skill was developed across 12 different journey items.

- **1999** - [CTO · Founder · technical director](https://portfolio.josedacosta.info/en/journey/celiane-founder.md) (entrepreneurship) - Confidence: 3/5
- **2001** - [BTS IG (IT Management)](https://portfolio.josedacosta.info/en/journey/bts-computer-science.md) (education) - Confidence: 2/5
- **2008** - [Junior Software Engineer · PHP Joomla Webmaster Developer](https://portfolio.josedacosta.info/en/journey/ministere-sante-webmaster.md) (experience) - Confidence: 3/5
- **2009** - [Software Engineer · PHP Zend Framework Developer](https://portfolio.josedacosta.info/en/journey/european-sourcing-engineer.md) (experience) - Confidence: 5/5
- **2013** - [Senior Software Engineer · Lead PHP Symfony Developer](https://portfolio.josedacosta.info/en/journey/medialeads-senior-engineer.md) (experience) - Confidence: 5/5
- **2016** - [Technical Project Manager · Co-founder · Early-Stage Startup](https://portfolio.josedacosta.info/en/journey/adspower-cofounder.md) (entrepreneurship) - Confidence: 4/5
- **2017** - [Senior Software Engineer · Lead PHP Magento Developer](https://portfolio.josedacosta.info/en/journey/smile-senior-engineer.md) (experience) - Confidence: 4/5
- **2019** - [Engineering Manager · Project Manager / Product Owner · Technical Lead](https://portfolio.josedacosta.info/en/journey/pichet-group.md) (experience) - Confidence: 5/5
- **2019** - [Technical Lead · Flows and Products: content and enterprise integration](https://portfolio.josedacosta.info/en/journey/pichet-technical-lead.md) (experience) - Confidence: 4/5
- **2020** - [Entrepreneur · Various Business Domains](https://portfolio.josedacosta.info/en/journey/auto-entrepreneur-jdc.md) (entrepreneurship) - Confidence: 5/5
- **2023** - [Master Expert in Software Engineering](https://portfolio.josedacosta.info/en/journey/master-software-engineering.md) (education) - Confidence: 5/5
- **2024** - [CTO · Founder · technical director](https://portfolio.josedacosta.info/en/journey/accenseo-founder.md) (entrepreneurship) - Confidence: 5/5

## Related achievements

- [Intelligent Accounting SaaS Platform](https://portfolio.josedacosta.info/en/achievements/plateforme-comptabilite-saas.md) - 234K-line SaaS platform: Next.js 16, React 19, TypeScript, 42 features, 382 API routes
- [SaaS platform for mortgage credit brokers powered by AI](https://portfolio.josedacosta.info/en/achievements/plateforme-saas-courtiers-credit-immobilier.md) - Built 211K-line multi-app SaaS platform with Next.js 16, React 19, TypeScript 5.9, and Prisma 7
- [AI Chat Export - Multi-Platform AI Conversation Export Extension](https://portfolio.josedacosta.info/en/achievements/ai-chat-export.md) - Built complete browser extension with React 19, TypeScript strict mode, and Vite
- [Gradient Generator - Advanced CSS Gradient Creation Tool](https://portfolio.josedacosta.info/en/achievements/gradient-generator-css.md) - Built complete SPA with Next.js 16, React 19, Zustand, Prisma 7, and OpenAI API integration
- [Atlassian Forge Developer - Intelligent IDE Plugin](https://portfolio.josedacosta.info/en/achievements/atlassian-forge-developer-ide-plugin.md) - Developed 9,120 lines of Kotlin code for IntelliJ Platform plugin with JVM/Java 21 runtime, Gradle Kotlin DSL, and SnakeYAML/Gson integration
- [Trade Show Community Portal Platform](https://portfolio.josedacosta.info/en/achievements/portail-communautaire-salons-professionnels.md) - Built WordPress corporate site with custom PHP, jQuery, and AJAX forms
- [European B2B Search Engine for Promotional Products (European Sourcing)](https://portfolio.josedacosta.info/en/achievements/moteur-de-recherche-europeen-b2b-objets-publicitaires.md) - Built 15+ interconnected sub-applications spanning PHP MVC custom, Symfony 2/3, AngularJS SPA, jQuery Mobile and PhoneGap/Cordova apps over 8 years
- [EuropeanTool - B2B Promotional Product Platform](https://portfolio.josedacosta.info/en/achievements/europeantool-plateforme-b2b.md) - Built 30+ interconnected PHP applications covering the entire B2B supply chain over 10 years
- [B2B Product Data Export Platform](https://portfolio.josedacosta.info/en/achievements/export-donnees-produits-b2b.md) - Built complete PHP MVC application with CLI batch processing, PrestaShop API integration, and concurrent export management - Developed end-to-end B2B export platform: Bootstrap/jQuery UI, PHP controllers, MySQL queries, CLI scripts, and API integration
- [Multi-Supplier Product Data Import System](https://portfolio.josedacosta.info/en/achievements/import-european-sourcing.md) - Built complete PHP import pipeline processing 254+ supplier catalogs across 120+ database tables
- [Food Truck & Mobile Concept Platform - French manufacturer (alias MCR)](https://portfolio.josedacosta.info/en/achievements/plateforme-food-truck-concepts-mobiles.md) - Shipped 129K lines across frontend, backend, admin, CMS extensions and AI tooling - 78 pages, 54 API endpoints, 133 database tables
- [Centralized Multilingual Translation Management Platform](https://portfolio.josedacosta.info/en/achievements/plateforme-gestion-traductions-multilingues.md) - Built complete Symfony 2 application with 3 controllers, 2 services, 15 routes, and inline AJAX editing
- [tailwindcss-obfuscator - Open Source CSS Obfuscation Tool](https://portfolio.josedacosta.info/en/achievements/tailwindcss-obfuscator.md) - Built complete npm package with 25 TypeScript modules, 5 bundler plugins, and CLI using Babel AST and PostCSS
- [Supplier Back-Office - B2B Self-Service Portal](https://portfolio.josedacosta.info/en/achievements/supplier-backoffice-european-sourcing.md) - Built complete 18K-line SPA with AngularJS, CoffeeScript, and Express.js consuming 35+ REST API endpoints
- [MagicPlaylist - Android Music Discovery & Playlist Generator](https://portfolio.josedacosta.info/en/achievements/magicplaylist-android-music-discovery.md) - Built native Android app with Kotlin, Jetpack Compose, integrating Shazam and Spotify APIs end-to-end
- [Collaborative Project Management Platform](https://portfolio.josedacosta.info/en/achievements/plateforme-gestion-projets-collaboratif.md) - Built 30K-line full-stack application with Java 17/Spring Boot backend and Angular 20/TypeScript frontend
- [E-Commerce Platform Redesign Magento Enterprise Edition (alias Fleurance Nature)](https://portfolio.josedacosta.info/en/achievements/refonte-ecommerce-magento-fleurancenature.md) - 60 custom Magento modules (1,040 PHP files), responsive theme across 3 storefronts, end-to-end ownership of backend + frontend
- [ETL Pipeline for Real Estate Listing Syndication (alias Ligneurs)](https://portfolio.josedacosta.info/en/achievements/pipeline-etl-syndication-immobiliere.md) - Sole technical owner over 4 years: PHP/Symfony, Akeneo PIM v2 integration, image processing, format generators, monitoring tooling
- [PIM Extranet for B2B Promotional Products Search Engine (European Sourcing)](https://portfolio.josedacosta.info/en/achievements/extranet-pim-b2b-objets-publicitaires.md) - PHP custom MVC then Symfony 3.1, Doctrine ORM, RabbitMQ async messaging, MySQL then PostgreSQL over 5+ years. Owned 229K lines across the Extranet v1, v2 Rebirth and Supplier BO (AngularJS SPA), front-to-back ownership
- [Flux - Supplier Data Synchronization](https://portfolio.josedacosta.info/en/achievements/flux-synchronisation-fournisseurs.md) - Built 37 connector classes for 30+ European suppliers handling 7 data formats across 8+ countries
- [E-Commerce Site Generator with Customization CMS (alias MyEasyWeb)](https://portfolio.josedacosta.info/en/achievements/generateur-sites-ecommerce-avec-cms.md) - Led 108K LOC codebase across 3 interconnected apps with 1,506 commits over 4+ years
- [AI Machine Learning SaaS Platform for Ad Optimization (alias AdsPower)](https://portfolio.josedacosta.info/en/achievements/plateforme-publicitaire-machine-learning.md) - Built full-stack platform with Symfony 3.2 backend, Angular 4/10 frontend, and ML pipelines

Interactive version with navigation: https://portfolio.josedacosta.info/en/skills/fullstack-development