Senior Full-Stack Engineer (.NET & React)

We are hiring on behalf of our client, a global innovator in fitness and wellness technology. Their mission is to empower people to live fit, strong, long, and happy lives by delivering integrated experiences to millions of members anytime, anywhere.
We are looking for a Senior Full-Stack Engineer (.NET & React) to join the Content Platform team, focused on building systems that power music-related experiences across the product ecosystem. In this role, you will design and develop APIs and backend services that support everything from instructor class planning to real-time music playback during workouts. This is a hands-on engineering role with strong ownership, where you will work on distributed systems, collaborate across teams, and directly impact user-facing features at scale.

Key takeaways:

Stack: C#, .NET, REST APIs, React/Vue, MongoDB, AWS (S3, SQS, Lambda), microservicesSalary: 23 000 PLN - 28 000 PLN gross on the Contract of Employment
Working model: Hybrid - 3 days/week from the office
Location: ul. Grzybowska 60, Warsaw
Recruitment process:
• A call with MOTIFE Recruiter
• Panel interviews with the team (coding, architecture, and cross-collaboration interviews, Hiring Manager meeting)
Responsibilities:

Backend Development & Architecture
• Design, build, and maintain scalable APIs and microservices supporting content and music-related features
• Develop systems for managing music catalogs, class planning tools, and platform integrations
• Ensure high performance, reliability, and scalability of backend services

Technical Excellence
• Write clean, maintainable, and well-tested code with a focus on long-term sustainability
• Drive best engineering practices, including CI/CD, automated testing, logging, and monitoring
• Continuously improve system architecture while avoiding unnecessary complexity

Collaboration & Delivery
• Partner closely with Product, Design, and QA to deliver high-quality features
• Actively participate in architecture discussions, code reviews, and technical planning
• Translate UI/UX requirements into reliable backend solutions

Engineering Culture
• Contribute to a culture of code quality, ownership, and continuous improvement
• Promote practices such as refactoring, pair programming, and iterative development
• Support knowledge sharing and help evolve engineering standards across the team

Requirements:

Technical Expertise
• 5+ years of professional software development experience
• Strong knowledge of C# and .NET ecosystem
• Experience building and maintaining RESTful APIs
• Solid understanding of asynchronous programming and multi-threading
• Experience with NoSQL databases (e.g., MongoDB)
• Familiarity with microservices architecture

Frontend & Platform Awareness
• Working knowledge of React, Vue.js, or similar frontend frameworks
• Understanding of system integration and API-driven development

Engineering Practices
• Experience with CI/CD pipelines, automated testing, and DevOps principles
• Understanding of Agile and Lean development methodologies
• Strong focus on code quality, maintainability, and scalability

Collaboration & Mindset
• Strong communication skills in English
• Ability to work effectively in cross-functional teams
• Comfortable working in fast-paced, evolving environments

Nice to Have
• Experience with Docker and Kubernetes
• Familiarity with AWS services (S3, SQS, Lambda)
• Experience with messaging systems (e.g., NServiceBus, RabbitMQ)

What we offer:
• 100% paid medical care
• Multisport
• Creative tax (KUP)
• Home office allowance
• MacBook Pro