Senior Full Stack Developer (70% Backend)

Senior Full Stack Developer

Build technology that helps millions of people change their lives

Every day, millions of people use Fitness22 products to get stronger, become healthier, and build habits that last.

Building products at that scale creates meaningful engineering challenges. Performance matters. Reliability matters. Architecture matters. And the systems you build directly affect the experience people have every day.

We’re looking for a Senior Full Stack Developer who wants to take ownership of those challenges and help us build products that work exceptionally well at scale.

Fitness22 is a profitable, bootstrapped product company that’s been building mobile fitness and wellness products since 2011, with more than 100 million downloads worldwide.

We’re a small team, which means engineers aren’t several layers removed from the product. You’ll work directly with Product, Design, Mobile, and Data, have real ownership over what you build, and see your work reach users quickly.

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.

Our stack

Node.js · TypeScript · React · PostgreSQL · MongoDB · AWS · Kubernetes

You don’t need experience with every technology in our stack. Strong engineering fundamentals and the ability to learn matter more than matching every tool.

What you’ll do

• Design and build backend services and APIs that support products used by millions.

• Solve technical challenges around performance, reliability, architecture, and scale.

• Build primarily with Node.js and TypeScript, and contribute to React applications when needed.

• Own technical problems from design through implementation and production.

• Collaborate with Product, Design, Mobile, and Data.

• Use modern AI tools as part of your development workflow.

What we’re looking for

• 4+ years of professional software development experience.

• Strong production experience with Node.js and TypeScript.

• Strong backend engineering fundamentals and experience building production systems and APIs.

• Full Stack experience and the ability to work with React when needed.

• Strong engineering judgment, ownership, and problem-solving skills.

• Excellent communication and collaboration skills.

Nice to have

• Experience with relational or NoSQL databases.

• AWS, GCP, or other cloud platforms.

• Kubernetes, microservices, distributed systems, or CI/CD.

• Mobile development experience.

• Degree in Computer Science, Engineering, or a related field.

Why join Fitness22?

Build products that help millions of people live healthier, stronger lives.

Work in a small engineering team where your decisions matter, your work reaches users quickly, and you can have real influence over both the technology and the product.