Case study · Rester Jeune
Build to grow. Simplify to last.
For four years, I led Rester Jeune’s technology: moving beyond ClickFunnels, building the product and team, launching the apps, absorbing peak demand—and ultimately handing over a simpler system with no dependency on me.
Rester Jeune
- Client
- Rester Jeune
- Scope
- Fractional CTO · SaaS · mobile · infrastructure · handover
- Timeline
- 2021 → 2025 · 4 ans
- Clément
- Clément SauvageProduct Engineer & Technical Lead
- Role
- Fractional CTO · Lead developer · Technical advisor
- Technology
- Stripe · Mux · React Native · PostgreSQL · Redis · Kajabi
The starting point
2021A solid business. A product it had outgrown.
Rester Jeune helps people over 50 build lasting movement, nutrition and wellbeing habits through the subscription-based RJFit method. By 2021, thousands already used the programme, but ClickFunnels was acting as website, product and back office. It could sell; it could no longer support the experience.
Founder and former professional rugby player Julien Hyardet did not want to become technical. He needed a dependable product and one person able to translate technical decisions into business consequences.
The need was not a new stack. It was technical leadership willing to own the choices.
The role
A fractional CTO at the intensity the business required.
The engagement evolved with the product: full-time to build, three days a week to operate, then one day a week to simplify and hand over.
Lead developer
Build the foundation, lead two front-end developers and an apprentice, then ship to production.
CTO
Choose the stack and vendors, arbitrate buy versus build, and plan capacity and costs.
Founder counsel
Connect every technical decision to member experience and business economics.
The trajectory
2021 → 2025Build, learn, then choose.
Move beyond ClickFunnels
Create a real SaaS platform for programmes, progress tracking, membership and recurring payments.
MVP → MLP
Move from a functional MVP to the minimum lovable product members want to open every morning.
Make mobile a product channel
Validate usage quickly with React Native, then move native as mobile becomes central to the experience.
Return to a market platform
Move to Kajabi once custom software no longer justified its fixed cost, without losing members or data.
Operations
Predictable peaks are still peaks.
January 1 and the September return multiply normal traffic. Monitoring, alerts, planned capacity and incident procedures made those days ordinary for members—precisely because the technical team treated them as exceptional.
Successful infrastructure is the infrastructure 75,000 members never notice.
The defining decision
Do not defend custom software on principle.
The proprietary platform had done its job: replace ClickFunnels, structure the product, launch the apps and reveal actual usage. Once Kajabi covered the now well-understood needs, maintaining custom software would mainly have preserved a technical territory. Reducing fixed costs had become the better business decision.
The handover
A clean exit is part of the mandate.
The final year was used to train a team member to operate Postgres, Redis and Metabase, then document access and procedures. They ran the system for several months before the final migration. When the engagement ended, nothing still depended on my presence.
Results
Growth without dependency debt.
Rester Jeune built its platform when it was necessary, learned from it, then returned to a controlled cost structure.
What this project demonstrates
Technology in service of the trajectory.
Speak business
Explain consequences instead of imposing the vocabulary of tools.
Know when to undo
Building and later recommending simplification are the same job.
End without dependency
A long engagement is also judged by how it ends.
Client testimonial
“Clément demonstrates exemplary professionalism and great rigor in his work. I am very satisfied with our collaboration and I have no hesitation in recommending him 100% for any task requiring a high level of skill and commitment.”