MeilleursAgents
Building everything, from the first server to a team of 30
Context. In April 2008, MeilleursAgents has no product, no code, and no engineering team. The ambition: estimate the value of every home in France, building by building, and simplify the real estate transaction. Nicolas Mussat is its first employee, six months before the website opens to the public.
Role. With Julien Cheyssial, the technical cofounder, he designs and builds the first version of all three products: the public valuation website, the back office that runs the business and the relationship with partner agencies, and the extranet for real estate agents. He chooses the stack (Python, PostgreSQL, React) and the hosting provider. Over nine years, he goes from lead developer to CTO, and grows the engineering team to 30 people.
- the valuation model: architecture, infrastructure, and the first POC, then leading the team that develops it
- the pivot, in 2015: from transaction sharing with selected agencies to a subscription for professionals (online storefront, client reviews, recent sales showcased), without shutting down the original model. From the decision to execution: product design, planning, technical delivery. In two years, partner agencies grow from 600 to over 4,500
- the move to the cloud, the same year: AWS and Google Cloud put in competition. Google Cloud chosen, simpler and at the cost of the bare-metal servers, while AWS’s proposed architecture cost three times as much
- the technical due diligence for the €7M round led by Piton Capital and Bpifrance, in 2016
Outcome. MeilleursAgents becomes France’s leading online real estate valuation platform: 1.8 million unique visitors and 10 million page views a month, 5,000 partner agencies. The company is acquired by Axel Springer in 2019.
The lesson for a CTO. A platform is built in stages: every early choice has to be able to evolve with the company. A pivot is carried out without breaking what brings in revenue. And infrastructure is judged on its cost and simplicity, not on how sophisticated its architecture is.
Prose
Cofounding the company, and building the platform that runs it
Context. In 2017, Arnaud Plas, Paul Michaux, Catherine Taurin, and Nicolas Mussat found Prose: personalized haircare, formulated for each customer after an online consultation, made to order, and delivered by subscription. An international company from day one: headquarters and factories in the US, its main market, and a research center in Paris. No e-commerce platform at the time can handle a 30-step consultation, a unique product per customer, and made-to-order manufacturing.
Role. Cofounder and CTO from 2017 to 2025, based in Paris. Nicolas Mussat chooses the whole stack (Python, React, PostgreSQL, Google Cloud, Kubernetes) and builds from scratch the platform that runs the company, from the consultation to the factory. He builds and leads an engineering team of 35: front-end and back-end engineers, product owners, DevOps, and data engineers.
- the consultation and the formulation algorithm: the first implementation of a model that combines machine learning and expert rules, refined with every customer’s feedback after use. More than 60 million prescriptions generated
- the subscription: the formula improves with every order, based on weather, pollution, new ingredients, and customer feedback. A rare model in personal care, where products are mostly bought one-off. The repeat rate runs 30 points above the industry average
- production and fulfilment: the software that runs the manufacturing of unique products on the automated lines of two factories, in Brooklyn and Los Angeles. The second machine, an improved version of the first, can produce up to 50,000 personalized products a day
- build or buy: build what Prose’s model made unique, buy the rest (inventory, forecasting, customer service)
- Singular: from an in-house tool to a complete personalization platform, which now carries Prose’s image as the leader in its field
Outcome. From three haircare products in 2017 to a full range: haircare and styling, supplements, skincare. 8.7 million customer profiles, more than 15 million products made to order, 500,000 five-star reviews, and $500M in lifetime sales. About 300 people, 160 of them in the factories, and $75M raised from Insight Partners and Forerunner Ventures. The made-to-order manufacturing platform is still unmatched in the industry.
The lesson for a CTO. Building rather than buying is justified where the company’s model exists nowhere else, and only there. When the product is physical, software doesn’t stop at the website: it runs all the way to the production line. And a subscription has to be earned: it holds because the product gets better with every order.
What the two have in common
- starting from zero: the product, the stack, the hosting, the team
- growing the technology and the team at the company’s pace
- building what makes the difference, buying the rest
- changing the model or the scale without breaking what brings in revenue
- leaving systems the team runs without outside help
Those are the instincts a fractional CTO or an interim CTO brings to your company.