Senior Backend Developer — Strategy Team F/H/X

Location: Colombelles, Normandie, fr

Employment Type: Standard

Company Description

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.

Job Description

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.

Qualifications

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

Additional Information

Interview Process

• HR / Talent Acquisition interview (45 min, video call) : Presentation of your career path, presentation of the recruitment context, discussion of your motivations
• Tech Lead & Staff or Engineering Manager interview (60 min, video call) : In-depth presentation of the team and how the tech team in Caen operates, culture, values
• Take-home case (1 week) + technical debrief with Tech Lead & Staff or EM (90 min, on site)
• Final culture & alignment interview with CTO (30 min, onsite) and team members (30 min, on site)

As an inclusive company, Veolia is committed to diversity and gives equal consideration to all applications, without discrimination.