Senior Full-Stack Developer

Senior Full-Stack Developer – .NET, Python & React

Découvrez exactement les compétences, l'expérience et les qualifications dont vous aurez besoin pour réussir dans ce rôle avant de postuler ci-dessous.

Paris, France | Hybrid

Permanent | Full-time

Build software for the energy transition

Our client is a fast-growing EnergyTech company developing software that helps renewable energy producers manage increasingly complex energy contracts and portfolios across European electricity markets.

As renewable generation continues to grow, energy markets are becoming more sophisticated. Our client is building technology that enables renewable energy producers to model, monitor and optimise their contracts and portfolios, helping accelerate the transition towards market-based energy revenues. We are looking for a Senior Full-Stack Developer to join a team of three experienced engineers and help build and scale this data-intensive, API-driven platform.

The role

This is a genuinely full-stack position, with a balanced focus across backend development, data processing and frontend engineering.

You will work with modern technologies including .NET 9, Python, React and Next.js, contributing to both new product development and the continuous improvement of the existing platform.

Your responsibilities

• Design and develop backend services using C#, ASP.NET Core and EF Core.
• Build Python-based APIs and data processing workflows using FastAPI and Pandas.
• Develop modern web interfaces using React, Next.js and TypeScript.
• Design and maintain reliable, scalable and clean software architectures.
• Optimise API performance and data processing across the platform.
• Work with PostgreSQL and data-intensive applications.
• Use .NET Aspire for development and distributed application orchestration.
• Work with modern observability tools including OpenTelemetry and Grafana.
• Troubleshoot, debug and profile applications across backend and frontend layers.
• Contribute to CI/CD, Docker-based development and engineering best practices.
• Participate in the team's IT support rotation.

Technology stack

• Backend: C# / .NET 9 / ASP.NET Core / Python / FastAPI
• Frontend: React / Next.js / TypeScript
• Data: PostgreSQL / Pandas
• Cloud & DevOps: Docker / CI/CD / .NET Aspire
• Observability: OpenTelemetry / Grafana

What we're looking for

You have 5+ years of full-stack development experience and are comfortable working across both frontend and backend technologies.

You bring

• Strong professional experience with C# / .NET.
• Strong experience with Python, ideally including FastAPI and Pandas.
• Solid knowledge of React, Next.js and TypeScript.
• Experience designing APIs and working with data-intensive applications.
• A good understanding of application performance and optimisation.
• Strong debugging and profiling capabilities.
• Experience working with modern software development practices.
• A pragmatic, root-cause-oriented approach to problem solving.
• The ability to work independently while collaborating closely with a small senior engineering team.
• English communication skills.

Nice to have

• Experience with OAuth2/OIDC or Keycloak.
• Experience with containerised environments and Docker.
• Knowledge of asynchronous or event-driven architectures.
• Experience with distributed systems and observability.
• Previous experience in EnergyTech, FinTech or another data-intensive industry.

What our client offers

• A key engineering position within a growing EnergyTech company.
• The opportunity to work on software directly supporting the European energy transition.
• A highly technical environment with a small team of experienced engineers.
• A flexible working model with regular face-to-face collaboration.
• Competitive fixed salary aligned with your experience.
• Performance-based variable compensation.
• Health insurance.
• Daily meal vouchers.
• Support with professional commuting expenses.
• Modern offices in Paris, 20th arrondissement.

Recruitment process

The process is designed to be fast and transparent:

1. Discovery Call – 30 minutes

An introductory conversation with the CEO to discuss your background, expectations and the