40folds
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All open roles
EngineeringFull-timeParis, FranceMid/Senior

Full-Stack Engineer

Our digital twins are only as useful as the product that carries them. You'll be one of the first engineers at 40folds, turning Bayesian models into software that CFOs and executive committees open before every big budget decision — from the data flowing in to the scenario screens they present in the boardroom.

Apply for this role

Your mission

  1. 01Shape the architecture of our modelling platform, from client data ingestion to scheduled model runs.
  2. 02Create the screens where executives compare scenarios, trade-offs and investment options.
  3. 03Make uncertainty readable: response curves, confidence bands and efficient frontiers that feel instant.
  4. 04Pair with our data scientists to move new modelling ideas from notebook to production.
  5. 05Keep the platform reliable and secure as we onboard larger clients.
  6. 06Help define how we build: code reviews, tooling and the engineering culture of a growing team.

You likely have

  • Several years shipping web products where you touched both the interface and the server side.
  • Solid TypeScript and React, a modern backend language, and SQL you are proud of.
  • Experience with cloud infrastructure and data-heavy or compute-heavy workloads.
  • Care for visual detail — you notice when a chart misleads.
  • The habit of finishing what you start and explaining your choices simply.

Bonus points

  • Python for data work, or exposure to probabilistic programming (PyMC, Stan, NumPyro).
  • Past work on analytics, planning or decision tools for business users.
  • Time spent in a small company where everyone wears several hats.

Probably not the right move if…

  • You want every requirement written down before touching a keyboard.
  • You would rather specialise in one layer of the stack.
  • Statistics and modelling leave you cold.
  • A changing weekly plan sounds stressful rather than exciting.

Life at 40folds

Salary and equity — A fair salary and a real stake in what we are building together.
Your setup, your choice — The hardware you need, plus a yearly budget for books, courses and conferences.
Tools that help you think — If a piece of software makes you sharper or faster, we cover it.
Office in Paris — A central base for working together, with flexibility when you need focus.
Time together — Regular team off-sites and dinners — and we always celebrate client wins.
Real responsibility — Direct line to the founders and a say in the company’s big decisions.
Ready to build with us?
A founder personally reviews each application.
Apply now