Freelancer profile translated to English.
Back to original languageAbout Sébastien
15 years of experiencein web development on **Ruby on Rails**.
I supportgrowing startups**, **SMEs**, and **scale-upsthat need a senior developer to take over andevolve an existing application(refactoring, performance, new features) or **design a robust business application**, from API to interface.
🛠Technical Stack
🎯What sets me apart
I'm not a dev who codes fast and moves on to the next project. My goal: asolid technical foundationon which you can build for years to come. Understanding the business before writing code, progressive and measurable deliveries, tested and maintainable code.
📞Need a senior Ruby on Rails developer for a strategic project?
Contact me, response within 1 hour!
French
Native or bilingual
English
Fluent
Can work on-site
Paris (up to 50km), Lyon (up to 50km), Nantes (up to 50km), Lille (up to 50km), Bordeaux (up to 50km)
Experience
- MipiseRuby on Rails Developer – Fullstack – Payments & ComplianceSOFTWARE PUBLISHINGJanuary 2025 - August 2025 (7 months)Paris, France→ Mission ObjectiveEvolve the payment engine of a fintech SaaS platform to integrate card payments and strengthen regulatory compliance (3DS2, KYC, 2FA).→ Achievements
- Development of a card payment API (Monext, Payplug) integrated into the existing transactional engine.
- Implementation of strong authentication (2FA + OTP) to secure sensitive access and transactions.
- Evolution of the transaction engine: reserves, reconciliations, reporting, and accounting follow-up.
- Fullstack contribution to the internal dashboard: front-end redesign (JavaScript, TypeScript, TailwindCSS) and integration of compliance and supervision tools.
- Continuous improvement of service performance and stability in a context of strong regulatory constraints.
→ Technical Stack:Ruby on Rails, Roda, PostgreSQL, Redis, JavaScript, TypeScript, TailwindCSS, REST APIs, RSpec, Minitest, GitHub Actions - GetaroundRuby on Rails Developer – Fullstack – Pricing & RankingTRANSPORTATIONApril 2022 - January 2025 (2 years and 9 months)Paris, France→ Mission ObjectiveEvolve the pricing and ranking engine of an international marketplace (Europe / US) to improve price accuracy, performance, and conversion.→ Achievements
- Evolution of the dynamic pricing engine: new pricing rules, adaptation by market and seasonality.
- Development of internal tools for Product & Data teams: price simulators, interactive dashboards, integration of data models.
- Use of feature flags and A/B tests to validate the impact of pricing changes before global deployment.
- Front-end contribution (React, TypeScript) on internal tools to improve UX and analysis reliability.
- Continuous optimization of backend performance and data consistency across markets.
→ Impact:Measurable improvement in conversion, increased price reliability, and direct revenue growth for the platform.→ Technical Stack:Ruby on Rails, PostgreSQL, Redis, React, TypeScript, REST APIs, RSpec, Feature Flags, A/B Testing - SOLOCALLead Ruby on Rails Developer – Fullstack – CRM & Digital CampaignsSOFTWARE PUBLISHINGApril 2020 - March 2022 (1 year and 11 months)Boulogne-Billancourt, France→ Mission ObjectiveDesign and evolve Solocal's digital tools forprofessional clientsto improve customer management, sales tracking, and marketing campaign performance.→ Achievements
- Design and development of a CRM dedicated to professional clients, centralizing data and interaction tracking.
*Development of interoperable APIswith internal services (Pages Jaunes, ClicRDV, centralized SSO authentication).- Front-end contributions (Angular) to deliver consistent, user-oriented fullstack features.
→ Impact:Improved productivity of sales teams, better centralization of customer data, and enhanced experience for Solocal's professional clients.→ Technical Stack:Ruby on Rails, Angular, PostgreSQL, APIs, Sidekiq, RSpec, CI/CD, GitHub Actions
Reviews
Gatsby
Créazéro
Reviewed on 1/22/2020
Very good experience: explanations, implementation, deadlines, everything was organized and respected to move forward perfectly with our project, even finishing a few days ahead of schedule!
T
Timothée
WizVille
Reviewed on 4/21/2018
We are happy to have worked with Sébastien over these 2 weeks, and have confirmed our desire to make the relationship permanent so that he becomes a full member of our technical team.
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Education
- MasterEpitech2013