Senior Full Stack Developer (70% Backend)

About Fitness22 Fitness22 is a profitable, bootstrapped product company that’s been helping millions of people build healthier lives since 2011. We create mobile fitness and wellness apps used by people around the world, combining great user experiences with cutting-edge technology. Our engineering team is small, highly collaborative, and focused on building products that people genuinely use every day. We move quickly, keep bureaucracy to a minimum, and give engineers real ownership over the systems they build. As we continue expanding our platform and investing in AI-powered experiences, we’re looking for a Senior Full Stack Developer to help shape the next generation of our products. About the role This is a backend-first role (approximately 70%) for an experienced Full Stack Developer who enjoys solving complex engineering challenges while still building polished React applications when needed. You’ll design and build scalable backend services that power our mobile products, contribute to modern web applications, and work closely with Product, Design, Mobile, and Data to deliver features from idea to production. You’ll have significant ownership over architecture and technical decisions, with the opportunity to influence how we build, ship, and scale our platform. Tech Stack Node.js TypeScript React PostgreSQL MongoDB AWS Kubernetes What you’ll do Design, build, and maintain scalable backend services and APIs using Node.js and TypeScript. Develop modern React applications and reusable UI components. Design data models and work with PostgreSQL and MongoDB to build reliable, high-performance systems. Build scalable infrastructure that supports rapid development, reliability, and future growth. Collaborate closely with Product, Design, Mobile, Data, and Marketing to deliver end-to-end features. Participate in architectural discussions, code reviews, and technical decision-making. Use modern AI tools as part of your daily development workflow and contribute to AI-powered features across our products. What we’re looking for 4+ years of professional experience building production applications with Node.js and TypeScript. Experience building modern React applications. Strong understanding of scalable backend architecture, APIs, and distributed systems. Hands-on experience with PostgreSQL and/or MongoDB. Experience working with cloud platforms such as AWS or GCP. Familiarity with Kubernetes is a plus. Passion for writing clean, maintainable, well-tested code. Excellent communication skills and the ability to collaborate effectively with cross-functional teams. Bachelor’s degree in Computer Science, Engineering, or equivalent practical experience. Nice to have Experience with CI/CD pipelines. Experience with microservices. Experience developing mobile applications. Why join Fitness22? Build products used by millions of people worldwide. Work in a small engineering team with high ownership and real influence. Ship quickly without unnecessary bureaucracy. Help shape AI-powered experiences across our products. Build products that help millions of people live healthier, stronger lives.