Sweep is looking for a Senior Fullstack Engineer (freelance) to work on our Sustainability Data Intelligence Platform.
Climate change is the defining issue of our time. Sweep builds a sustainability data intelligence platform used by major enterprises to track greenhouse gas emissions, meet regulatory requirements, and drive real decarbonization. We're a B Corporation, and we mean it.
Ok, sounds promising. What will I be doing?
As a Senior Fullstack Engineer, you'll own features end-to-end, from data models and backend systems to the interfaces that make sustainability data actionable. You'll work at the heart of our core product, alongside a team that cares deeply about quality and impact.
What you'll be working on:
Build and own core product features
- Design and implement full-stack features from the ground up: database schema, backend logic, GraphQL API, and React/TypeScript UI
- Take full ownership of significant parts of the system: reliability, performance, and long-term maintainability are yours to drive
- Participate in every stage of the development lifecycle, from design and implementation to rollout and smooth operation in production
- Contribute to and challenge our technical architecture as we scale
Bring genuine backend depth
- Design robust data models and schemas built to perform at scale
- Build and operate backend services, including background jobs, async pipelines, and integrations with third-party systems
- Own observability: instrument systems, define meaningful metrics, and respond to incidents with confidence
- Identify and address security risks proactively from API design to infrastructure exposure
- Automate deployments via our CI/CD systems and continuously improve development processes
Work with AI as a day-to-day accelerator
- Leverage AI tools actively in your workflow, from code generation and review to debugging and documentation, to move faster without compromising quality
- Contribute to how we integrate AI-assisted development practices across the engineering team
- Stay curious about emerging AI capabilities and bring new ideas on how we can use them to ship better, faster
Be a team force multiplier
- Lead technical design on significant features and share your experience openly
- Review pull requests with rigour and care, raising the bar for the whole team
- Participate actively in team rituals: stand-ups, planning, retros
- Contribute to our culture of quality: incremental, well-tested, observable changes
Pursue quality, always
- Champion clean code, solid test coverage, and strong engineering practices
- Improve processes and methodologies to reach the highest standards
- Bring excellence to your own work and help others do the same
That sounds just right for me. What do I need to bring?
Glad you asked. This is who we’re looking for:
5+ years of experience shipping product across the full stack, with strong backend foundations
Fluent in React/TypeScript on the frontend; deep expertise in relational databases, distributed systems, observability, and security on the backend
Comfortable owning features end-to-end with autonomy and clear communication
Strong plus: Ruby on Rails experience in a high-scale production environment
You write clean, well-tested code and take genuine ownership of your work
Practical Details
Hybrid or Remote. Offices in Paris, London, Montpellier, and Denver
Start date: ASAP
Duration: Long-term collaboration, renewable
Rate: 520€