Matthieu GuirlingerGet in touch
Portrait of Matthieu Guirlinger

Matthieu Guirlinger · Remote · Grand Est · Luxembourg

Freelance Tech Lead, from architecture to production.

15 years designing and building web projects for large organisations and public-sector bodies.

Let’s talk about your projectSee my work

Available from January 2027 · contract or project

I’ve worked on their projects, at agencies or as part of their teams

  • Région Île-de-France
  • VNF
  • SNCF
  • Bouygues Construction
  • BNP Paribas
  • Ligier
  • RATP
  • Pickup
  • France Digitale
  • Lonsdale
  • IN&FI Crédits
  • Sofidy
  • Solidarités International

Where I can help

A turnkey AI agent project? For a fixed-price project rather than a contract, head to Hexalor.Coming soon

Building with AI agents, without losing control of the code

I work with agents every day (Claude Code, Codex) and roll them out to teams with the framework they need: a harness that makes agents predictable, verifiable and safe. Teams move faster without lowering their standards.

  • Harness engineering

    I start with a simple harness that improves and grows session after session, so agents work with the same context as your team.

    • AGENTS.md
    • CLAUDE.md
    • Domain glossary
    • Architecture decision records
    • Code conventions

  • Skill-based workflows

    Review on two axes: code standards and fidelity to the functional need.

    1. Business alignment
    2. Vertical-slice tickets
    3. Test-first
    4. Review

  • Deterministic guardrails

    The model is probabilistic, the checks are not: the agent proposes, they decide.

    • Types
    • Tests
    • Browser access
    • Hooks
    • Blocking CI

  • Code that stays maintainable

    Producing code has never been faster, and architecture choices have never mattered more: they are what keeps the code readable and easy to evolve.

    • Well-scoped modules
    • Simple interfaces
    • Architecture reviews
    • Human review of critical code
  • Rollout in your team
  • Workflow audit
  • Developer coaching
Let's talk

Selected projects

  • Automotive

    WordPress · Roots · Node.js · Meilisearch    2026 · Automotive
  • Humanitarian

    Laravel · Vue.js · PostgreSQL · Twilio    2026 · Humanitarian
  • Digital

    LangGraph · LangChain · TypeScript    2026 · Digital
  • Insurance

    NestJS · Next.js · PostgreSQL    2025 · Insurance
  • Luxury

    Next.js · tRPC · PostgreSQL    2025 · Luxury
  • Public sector

    Next.js · WordPress · Auth0    2024 · Public sector
  • Automotive

    Next.js · Node.js · GraphQL    2023 · Automotive
  • Finance

    Next.js · React Native · Node.js · WordPress    2022 · Finance

Multisite for a car manufacturer

A car manufacturer wanted to bring its country websites onto a single platform, with its vehicles, its dealer network and its leads connected to Salesforce.

Role
Tech Leadat unflux
Sector
Automotive
Year
2026
Outcome
13 country sites created in 2 days from a template: opening a new country is no longer a technical project
Stack
  • WordPress
  • Roots
  • Node.js
  • Meilisearch

Key points

  • WordPress multisite: 13 country sites in 19 languages, a site for professional customers and dealer microsites on dedicated domains
  • Custom multisite plugin: central network management and new sites created from distinct templates (country site, professional site, dealer microsite)
  • Roots Radicle foundation, structured like a Laravel application (Acorn, Blade, Eloquent), and a custom page builder with ACF Flexible Content (30 blocks)
  • New and used vehicle search with Meilisearch, synced from Salesforce by CRON jobs
  • 8 lead forms, each with its own structure, sent to Salesforce through a Node.js microservice
  • Dealer network: map with Meilisearch-powered search and a page per dealership
Discuss a similar project

WhatsApp bot for a humanitarian NGO

Solidarités International builds Solisbot, a WhatsApp bot that NGOs use to stay in touch with the communities they support. The team, spread across several contractors, needed a shared framework: quality tooling, a branching strategy and a review process. It also needed a technical lead to take over and approve a large business feature: tracking WhatsApp spending.

www.solis-bot.fr
Role
Tech Leadpro bono via Share-it
Sector
Humanitarian
Year
2026
Outcome
A properly tooled team sharing one review process, and NGOs tracking their WhatsApp budget number by number
Stack
  • Laravel
  • Vue.js
  • PostgreSQL
  • Twilio

Key points

  • Led the development team: every pull request reviewed and approved before merge
  • Introduced git flow: one branch per feature, release and fix, and made rebasing clear for the whole team
  • Linters brought back into working order (ESLint, Prettier, Laravel Pint) and run automatically before every commit with Husky, alongside continuous integration
  • Took over and approved the spending tracker: WhatsApp spending calculated per number and reconciled with the Twilio invoice
  • Hardened that feature: unit tests on the calculations, fixes, documentation for the team and Laravel scheduled tasks set up
  • Automated deployments to staging environments: image build, transfer to the server and migrations in a single command
Discuss a similar project

AI sales prospecting agent

Spot sales opportunities before competitors do: public tenders, but also company signals that point to a need, without spending hours on it every morning.

Role
Tech Lead
Sector
Digital
Year
2026
Outcome
A daily watch that takes minutes to read: only qualified opportunities reach the sales team, which keeps the final say
Stack
  • LangGraph
  • LangChain
  • TypeScript

Key points

  • Public tender monitoring in France, Luxembourg and across Europe (BOAMP, Luxembourg’s public procurement portal, TED): collection, deduplication and a first pass by CPV codes and keywords
  • Renewals anticipated: awarded contracts are tracked to spot those nearing their end, before the new tender is even published
  • Weak-signal detection on companies in Luxembourg and the Grand Est region: new companies, funding rounds, tech hiring, appointments
  • LLM qualification: relevance score, budget and duration extracted, reasoned verdict (pursue, watch, drop)
  • Human-in-the-loop: the sales team confirms each opportunity before any outreach or tender response, and its choices are used to refine the sorting criteria
  • Daily report sent by email and to the team’s messaging app
Discuss a similar project

Extranet for an insurance broker

An employee benefits broker wanted to give its corporate clients direct access to their claims, payments and DSN payroll declarations.

Role
Tech Leadat unflux
Sector
Insurance
Year
2025
Outcome
Time saved for account managers, better visibility for clients: claims filed and tracked online, no re-keying
Stack
  • NestJS
  • Next.js
  • PostgreSQL

Key points

  • Client portal and internal account-manager portal in Next.js, two NestJS APIs, in a monorepo
  • Open-source insurance software integrated through an adapter layer: GraphQL for reads, REST for writes
  • Online claim filing (sick leave, disability, death) with supporting document upload, sent straight to the insurance software
  • Payment and DSN flow tracking per company, with PDF and CSV export
  • Several companies per account, fine-grained permissions shared by front end and API, personal data anonymised according to the user's rights
  • HDS-certified hosting for health data: antivirus scan on every upload, audit log, sessions hardened after a penetration test
  • Over 800 automated tests, blocking SonarQube gate, SigNoz observability (OpenTelemetry) and Sentry error tracking
Discuss a similar project

Learning platform for a foundation

The foundation of a luxury house wanted a tool for its programmes passing on craft skills, run in classrooms by artisans alongside teachers.

Role
Tech Leadat unflux
Sector
Luxury
Year
2025
Outcome
A platform used in hundreds of schools, with thousands of pupils
Stack
  • Next.js
  • tRPC
  • PostgreSQL

Key points

  • Prototype delivered in one week, then a production foundation built from scratch: Turborepo monorepo, two Next.js applications, end-to-end typed tRPC API
  • Each school year set up by CSV import of schools, classes and users, then purged at year end
  • Photos and documents stored on S3: chunked upload of large files and bulk download as ZIP
  • Personal data minimised: inactive accounts deleted automatically after one year
  • Security: media access restricted by user permissions, files checked by their actual content, isolated back office with its own accounts and Microsoft Entra ID SSO
  • BullMQ queues on Redis and scheduled jobs in a dedicated service
Discuss a similar project

Events app for a business district

The public body that runs a major business district wanted an app to bring its major events to life: a microsite for each event, open to employees, students and residents, with sign-up, teams and inter-company competitions.

Role
Tech Leadat unflux
Sector
Public sector
Year
2024
Outcome
Every new event gets its microsite with no technical work: created from the back office, immediately editable by its organiser and published in the app
Stack
  • Next.js
  • WordPress
  • Auth0

Key points

  • Headless architecture: a WordPress multisite network with one subsite per event, an installable Next.js app (PWA) and a back office to run the events
  • Automated microsite creation: the back office creates the WordPress subsite through the REST API, hands it over to the organiser and manages shared settings (home page, footer, colours and visuals for each event)
  • WordPress multisite foundation, with a custom page builder using ACF Flexible Content (22 blocks)
  • App installable on mobile (PWA) with push notifications (WonderPush), switched on from the signed-in area and tied to each user’s account
  • Signed-in area secured by Auth0: profile and team management, competition tracking
  • Eco-design approach following the French RGESN framework: 70% of criteria met
Discuss a similar project

Configurator and online sales

A car manufacturer wanted its customers to configure their vehicle, pick a dealer and reserve online, in every country it sells in.

Role
Tech Leadat unflux
Sector
Automotive
Year
2023
Outcome
An online sales channel for the dealer network, rolled out to 18 countries
Stack
  • Next.js
  • Node.js
  • GraphQL

Key points

  • End-to-end journey: vehicle configuration, dealer selection on a map, services, online deposit payment
  • Online financing simulation and application with a banking partner
  • Customer account with passwordless login, saved configurations and order tracking
  • Consumer and professional journeys, promo codes, ordering enabled per country and per vehicle
  • A single codebase rolled out to 18 countries and around thirty languages
  • Node.js microservice architecture over GraphQL (catalogue, orders, accounts, notifications), with country-specific payment methods
  • Vehicle visuals generated dynamically server-side for every option chosen, by layering images
Discuss a similar project

Web and mobile platform for a network of credit brokers

A network of franchised credit brokers wanted a website that turns visitors into loan requests, sends them to the right broker near them and gives every agency its own showcase.

Role
Tech Leadat unflux
Sector
Finance
Year
2022
Outcome
A complete digital ecosystem, from the website to the mobile app, where every loan request is qualified online, then passed to the nearest broker licensed for the product
Stack
  • Next.js
  • React Native
  • Node.js
  • WordPress

Key points

  • Headless architecture: editorial content in WordPress, a Next.js website, Node.js microservices for loan requests and job offers, and a mobile app
  • Loan calculators: monthly payments with an amortisation table, borrowing capacity and notary fees based on the official scale, with rates managed from the back office
  • Multi-step loan request forms, adapted to each type of project: mortgage, debt consolidation, business loan, personal loan
  • Geolocated agency search with Meilisearch: every request goes to the nearest broker licensed for the product
  • Integration with the client’s CRM: at the end of the journey, every lead lands there automatically with all the qualification data collected
  • Microsites for the franchised brokers: opening hours, team, customer reviews, news and a form wired straight to the agency
  • React Native mobile app published on iOS and Android: calculators, agency search on a map, referrals and push notifications
Discuss a similar project

Career

  1. EixowebFounder & full-stack developerGrand Est · Luxembourg2013 — 2018
  2. af83Lead developerParis · remote2018 — 2020
  3. unfluxTech LeadParis · remote2020 — 2026
  4. IndependentFreelance Tech LeadRemote · Grand Est · Luxembourg2027

CNAM Lorraine · Software Architect & Designer degree2013

Understand, decide, build

I am accountable for the project's technical consistency, from the first architecture choices to changes in production. That happens in the code, and in conversation: with the client and business teams to understand the need, with the team to decide together, with external partners to connect the pieces, coordinate integrations and keep the whole thing coherent.

  • With the client and business teams

    Workshops, trade-offs, estimates: I translate business needs into technical choices, and make those choices clear to everyone.

  • With the team

    Code review, standards, documentation, upskilling: a team that ships, grows, and stays autonomous after I leave.

  • With partners

    Vendors, agencies, IT teams: I frame interfaces and integrations, all the way to acceptance testing.

  • In the code

    Architecture, critical parts and delivery: breaking down the work, holding priorities and a steady release pace. I stay hands-on every day.

Frequently asked questions

What kind of engagements do you take on?

Tech Lead or senior developer contracts: joining an existing team, or starting a project from scratch on my own. Also code audits and helping teams move to AI-assisted development. Within a team, I bring a technical framework and help everyone level up.

Can you step in for short engagements?

Yes. Alongside longer contracts, I take on short needs: a code or architecture audit, a review of a technical decision before committing to it, unblocking a specific problem, setting up a harness for working with AI agents, or a few days a month supporting a team.

Do you work remotely or on site?

Mostly remotely, with occasional trips to Paris, the Grand Est region and Luxembourg.

Do you work in Luxembourg?

Yes. Based in Moselle, close to the border, I work with Luxembourg clients, remotely as well as on site.

What happens at the end of the engagement?

I prepare the handover from day one rather than in the last week: documented architecture decisions, reviewed and tested code, written conventions, and developers who took part in the choices. When I leave, the team knows the project and can keep evolving it without depending on me.

Can you take over an existing project?

Yes. I start with a code and architecture audit to understand what holds up and what slows things down, then propose a prioritised plan: what we fix right away, what we evolve, and what we leave as it is. The goal is to get the project back on track without rewriting everything.

How do you handle security?

With a security-by-design approach: least-privilege access, secrets management, input validation, monitored dependencies, code review and automated tests. For AI agents, add tools with restricted permissions, human approval of sensitive actions, and control over the data sent to models.

Do you work with the public sector?

Yes. I have led several projects for public bodies and know their requirements: accessibility (RGAA), eco-design (RGESN), GDPR and public procurement. I can also support you on the client side of your tenders: drafting the technical specifications, then reviewing the bids.

A project to scope, a team to strengthen?

A few lines about your context are enough. I reply within 24 hours to set up a first 30-minute call, with no commitment.

Write a messageForm · reply within 24 hours

Let’s talk about your project

A few lines are enough. I reply within 24 hours on weekdays.

Context, constraints, timeline: whatever you can share.

Your details are only used to reply to you. Personal data

Message sentThank you. I reply within 24 hours on weekdays.