Senior Backend Developer - Strategy Team H/F - Flexcity

At Flexcity, we help the European power system become smarter, more flexible and more sustainable by connecting industrial assets (batteries, e-boilers, heat pumps, data centers...) to energy markets.
A subsidiary of Veolia Group, we combine scale-up agility with the stability of a global leader. At Flexcity, tech is a business driver, powering optimization and financial performance across Europe.

As a Senior Backend Developer F/H/X in the Strategy team, you will build the systems that optimize asset behavior and maximize €/MWh value through fully automated decision-making.

The team works at the intersection of backend engineering and data science, powering forecasting models, MILP optimizers, simulations and large-scale historical data pipelines. Your work directly improves financial outcomes for clients and Flexcity.

You will work end-to-end with a Product Manager and Engineering Manager in a high-autonomy feature team.

Your role focuses on:

- Backend Development (80%)
- Build backend services powering optimization, forecasting and decision engines.
- Design scalable pipelines handling large datasets and computational workloads.
- Own features from design to production monitoring.

- Team & Engineering Improvement (10%)
- Improve engineering standards, workflows and technical quality.
- Contribute to a strong culture of craftsmanship and continuous improvement.

- Technical Leadership (10%)
- Partner with Product Managers on feasibility, scope and trade-offs.
- Ensure architectural consistency and long-term system quality.

You are a senior backend engineer with 15+ years of experience building scalable systems, ideally in data-intensive, optimization-driven or algorithm-heavy environments.

Technical Knowledge & Skills

- Strong backend engineering and system design expertise.
- Experience with or strong interest in distributed systems, data pipelines or optimization engines.
- Comfort working on complex, computation-heavy production systems.
- Fluent in French and professional English.

Personal Qualities

- Analytical, ownership-driven and solution-oriented mindset.
- Strong communication and collaboration skills.
- Curious engineer with high technical standards.
- Comfortable in fast-moving, evolving environments.

Tech Stack

We use a modern, well-crafted tech stack that emphasizes clean architecture, reliability and developer excellence.

- Languages: Kotlin + SpringBoot, Go, Python
- Hexagonal architecture / Domain-Driven Design (DDD)
- Google Cloud Platform (GCP) / Kubernetes
- Pub/Sub
- PostgreSQL
- React
- GitLab
- Grafana Observability Stack

Benefits

- One tech conference per year (fully covered)
- Medium subscription & O'Reilly access
- Technical books & learning resources
- 5% of your time dedicated to exploration & learning
- Hybrid work model

• Python
• Clean
• Kotlin