Senior Software Engineer

Engineering Team

At Zefir, our Engineering Team is the driving force behind our mission to accelerate life changes. Growing rapidly from 9 to 30+ engineers, we don't just write code—we solve meaningful problems for our customers.

From ideation to launch and beyond, engineers at Zefir take full ownership of their work, ensuring that every feature delivers the expected impact. We leverage LLM-based development workflows and shared best practices to automate repetitive tasks, allowing us to keep our codebase lean, scalable, and built for speed.

Responsibilities/Mission

• Develop and deploy robust, high-performance APIs using Node.js (TypeScript), Nest.js, and GraphQL.

• Build intuitive frontend applications with React.js and Next.js, delivering outstanding user experiences.

• Collaborate closely with Product Managers and cross-functional teams (Operations, Growth, Brand) to prioritize features and deliver key objectives.

• Own the full lifecycle of features from ideation and design through implementation, deployment, and performance monitoring.

• Write clean, maintainable, thoroughly-tested code to ensure fast deployments and continuous improvement.

• Implement comprehensive end-to-end (E2E) tests to ensure reliability and reduce code review cycles.

• Proactively contribute to strategic decisions about the future direction of our web applications and infrastructure.

• Leverage LLM-based libraries and implement key AI-driven functionalities (RAG, memory, agentic workflows) using stacks like Pinecone and Langchain.

Qualification

• Entrepreneurial mindset with a demonstrated ability to turn ambitious ideas into practical solutions.

• Excellent problem-solving skills, with the ability to quickly evaluate and recommend effective technological solutions.

• Highly collaborative, open-minded, and comfortable working closely with diverse teams.

• Ambitious, performance-oriented, and maintains a positive attitude.

• Fluent in English for clear and effective communication.

Benefits

• Competitive salary : You can run your own simulation with our salary calculator.

• BSPCE (Stock Options) : Available for everyone, with monthly vesting after year one, over a 4-year period.

• Healthcare plan : Full coverage with Alan for team members, their partners, and children.

• Office in Le Peletier, Paris (9th arrondissement) : With flexible remote work options.

• Swile meal card : €11 per worked day.

• Swile mobility card : €42/month to support sustainable transportation (metro, carpooling, biking…).

• Team events : Monthly mixers to connect and share good times, and quarterly all hands to celebrate wins across the company.

Our Operating Principles

Steep Mountains Are Steep: Setting ambitious goals and working hard to achieve them.

Ride Reality: Actively seeking challenges and thriving by adapting flexibly to changes.

Play for the Front of the Jersey: Prioritizing team success over individual recognition.

Application & Process

We welcome applications from anyone, regardless of background, gender, sexual orientation, religion, age, or experience. Our team values authenticity and diverse perspectives.

For all roles, our interview process emphasizes hands-on exercises, case studies, or discussions about specific examples of your previous work. We ensure objectives and expectations are clearly communicated at every step.