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Nicolas Filzi

Fractional CTO & Product Engineer

One AI-enabled senior operator. Stack-agnostic, tool-agnostic, AI-augmented engineering from strategy to production code — for startups, scale-ups and non-tech businesses.

10+
Years shipping
Production systems since 2016
10+
Clients served
Startups to hospitals
3.5y
Longest engagement
Platform built & run end to end
8y
Teaching engineers
Le Wagon · 10+ cities

Profile

I've been turning ideas into production systems for over a decade — backends, platforms, APIs, AI pipelines. The kind of code that runs businesses, not just demos.

Along the way I spent 8 years teaching engineers at Le Wagon across Amsterdam, Tokyo, Nantes and Copenhagen. Teaching thousands of students to think about data, architecture and product didn't make me less of a builder — it made me a sharper one.

Today I work as a fractional CTO and product engineer for teams that need senior firepower without the agency overhead or the full-time ramp-up. I embed in your team — to untangle your problems and bring your ideas to life.

Expertise

Backend & Data
Ruby on Rails · Python · PostgreSQL · APIs · Data modeling · Real-time systems
Frontend & Mobile
JavaScript · TypeScript · React · React Native · Expo · Tailwind · Stimulus
AI / LLM
LLM pipelines · AI agents · LLM search & enrichment · Workflow automation
Leadership
Fractional CTO · Architecture · Code review · Mentoring & pairing · Vendor management

How I can help

Build
Full-stack product engineering — features, infrastructure, integrations, AI/LLM pipelines.
Lead
Fractional CTO — architecture, hiring, process, technical direction.
Lead + Build
Both roles, one person — technical direction and the strongest builder on the project.
Solve
Scoped engagements — audits, architecture reviews, rescue missions, second opinions.

Selected work

High StickersLead
~3 yrs

Rebuilt a 10-year e-commerce platform so well the founder became its top code contributor.

30k users migrated10k orders preservedRails · Stripe · Pennylane
PAJ by ImparatoLead + Build
Ongoing

Shaped a theatre-discovery platform from zero — product, architecture, AI-powered search, a team of 4.

787 classification dims500+ plays enrichedRails · React · Mistral AI
Iris GalerieLead + Build
Ongoing

API tech lead connecting ERP, mobile and desktop systems across 150+ points of sale worldwide.

56% of API commits12–16 people coordinated150+ galleries
KoudetatBuild
2 yrs

From concept to streaming platform as part-time CTO — product and tech strategy in one seat.

Part-time CTOStreaming platform builtServer → front end
Plancton by PimpantLead
3.5 yrs

1,000+ personalised kids’ science magazines shipped monthly — owned the platform end to end.

1,000+ magazines / mo3.5-yr engagementMentored a junior dev
CHU Nantes · Astreinte VitaleBuild
Delivered

Replaced paper call sheets and manual phone cascades for hospital emergency teams.

24/7 critical coveragePublic healthcareReliability-first
Guest SuiteSolve
Delivered

A CEO’s fast-moving ideas shipped as production tools every two weeks — no overhead.

2-week max turnaroundProduction toolsSaaS
AsmodeeBuild
Delivered

Daily intelligence on every crowdfunding campaign in the market — raw data to dashboards a team acts on.

BI platform builtDaily dashboardsNon-technical readers

What clients say

While he may have had the highest hourly rate I’ve ever paid, he ended up costing me the least overall, due to his speed and effectiveness.

Emmanuel · CEO @ High Stickers

He gets it quickly. He delivers quickly. And he delivers quality.

Thomas · CEO @ Guest Suite

His blend of business vision and coding talent makes him a key asset to any team.

Valentin · CEO @ Koudetat

Ventures & teaching

Founderpepline.ai — my own SaaS: lead-facing AI agents that retire the contact form. They interview inbound prospects, qualify them against your rules, and hand back a scoped brief — in beta.
Co-founderstellaire.studio — a Nantes startup studio taking founders from idea to market. I bring the product & tech side, from idea validation through MVP and go-to-market.
2016–2022Lead teacher, Le Wagon — bootcamp instructor and curriculum contributor across 10+ cities worldwide. Thousands of engineers taught.
2019–2021Le Wagon franchise co-owner — Nantes & Rennes — ran the franchise: B2C growth (workshops, events, paid marketing) and partnerships with schools, businesses & incubators. Grew earnings 50%+ two years running, then sold it back to Le Wagon HQ.
Since 2016Shipping in production — backends, APIs, e-commerce, mobile and AI pipelines for startups, scale-ups, hospitals and non-tech businesses.

How I work

  • Building the wrong thing well is the most expensive mistake in tech — business context first, architecture second.
  • You’ll see progress every week, not every quarter. Scope tight, ship real, measure, iterate.
  • You’re paying for judgment, not just execution — I’ll flag the risk no one’s talking about.
  • You own everything at the end — code, infrastructure, docs. Built for your autonomy, not dependency.