Senior Full-Stack Engineer - RoR, Next.js & Growth (LATAM)

About the Role

This is a contractor position through X-Team. We are seeking a Senior Full-Stack Engineer on behalf of a top global nutrition and fitness tracking platform used by millions of users worldwide. In this role, you will join the web growth team working alongside a Staff Web Engineer within a cross-functional squad (QA, Mobile, Backend, Product).

You will own critical feature launches across Rails, Next.js, and Node.js microservices, architecting high-converting web experiences, refactoring technical debt, and leveraging AI tools like Claude to drive daily development velocity and support aggressive web growth and SEO initiatives.

Key Responsibilities

Architect, build, and optimize high-converting web features, landing pages, and web flows targeting web growth and SEO performance using Next.js and Rails. Develop end-to-end features spanning Next.js frontends, Node.js middle-tier services, and Rails backends powered by REST and GraphQL APIs. Model and query data efficiently across MySQL, MongoDB, DynamoDB, and Redis caching layers.

Own the testing lifecycle for your code by writing automated unit/integration tests and conducting browser automation checks prior to QA handover. Integrate AI tools like Claude into daily coding, refactoring, and test generation workflows to maintain high delivery speed. Contribute to sprint planning, technical debt refactoring, and deployment activities while maintaining code quality and personal ownership.

Must Have Core Experience: Senior-level commercial experience developing full-stack web applications using Ruby on Rails, Next.js, and Node.js. Frontend & API Technologies: Expertise in TypeScript/JavaScript, Next.js, REST APIs, and GraphQL. Database & Architecture: Strong experience modeling and querying data across relational (MySQL) and NoSQL/Caching layers (MongoDB, DynamoDB, Redis).

Quality & AI Integration: Hands-on experience with self-directed testing practices (unit, integration, and browser automation) and daily use of AI-assisted development tools (e.g., Claude). Mindset & Way of Working: Self-starter autonomy, a generalist mindset, strong personal quality ownership, and high adaptability in cross-functional squad environments.

Design Collaboration: Experience working with design assets and systems in Figma. Logistics: Remote position based in LATAM with strong working hours overlap with US time zones.

Nice to Have

AWS Cloud Infrastructure experience. Background in SEO optimization and user acquisition growth strategies. Experience collaborating closely with mobile, backend, and dedicated QA teams in a cross-functional setup.