Senior Fullstack Engineer (Freelance)

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

• Solid experience with Ruby on Rails in a high-scale production environment is a must

• 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

• 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€