FullStack .NET Developer (React)

OPTIVEUM

7d • Hybrid

About The Position

Optiveum is a boutique talent advisory firm. We help our clients build high-performance technology teams that move the needle. We are currently looking for a Senior FullStack .NET Developer for our client—a fast-growing US-based leader in the Financial Technology sector. With a major engineering hub in Warsaw, they are blending American innovation and "move-fast" culture with top-tier Polish engineering talent. You’ll be joining an environment that skips the bureaucracy in favor of high ownership, architectural excellence, and a product-first mindset.

As a Senior FullStack Engineer, you aren’t just executing tickets; you are a product builder. You will bridge the gap between robust, high-scale backend services and modern, highly interactive user interfaces. This role is perfect for someone who thrives in a fast-paced US tech culture, enjoys solving complex distributed systems puzzles, and cares deeply about delivering a world-class User Experience (UX).

Requirements

• 5+ years of experience in .NET (.NET 6/8+) and C#.
• Expertise in building RESTful APIs and event-driven architectures.
• Solid experience with React and TypeScript.
• Familiarity with state management (Redux, Zustand, or React Query).
• Practical experience with Azure (App Services, Functions, Service Bus, Cosmos DB/SQL).
• Strong skills in SQL Server and Entity Framework Core.
• Hands-on experience with Docker, Kubernetes, and CI/CD pipelines (Azure DevOps/GitHub Actions).
• Excellent English (C1) – essential for daily collaboration with the US team.

Nice To Haves

• Experience in high-growth FinTech, WealthTech, or high-frequency trading environments.
• Knowledge of testing frameworks (xUnit, Jest/Cypress).
• Familiarity with Web Performance optimization and Accessibility (WCAG).

Responsibilities

• Own features end-to-end, from database schema and API design to the final React component.
• Contribute to the evolution of a Cloud-Native microservices architecture on Azure, designed to handle global traffic.
• Maintain high standards (SOLID, Clean Code, Design Patterns) while maintaining the velocity needed for a competitive US market.
• Drive the development of responsive, high-performance web applications using React.
• Partner closely with US-based Product Managers and Stakeholders to translate vision into scalable technical reality.
• Lead by example through Code Reviews and knowledge sharing, helping elevate the Warsaw engineering hub.

Benefits

• Access to the latest tech—we operate on the "bleeding edge" of .NET and React.
• Modern Warsaw Office: A vibrant, well-located hub for collaboration, combined with a flexible hybrid/remote policy.
• Competitive Compensation: 18.000 - 25000 PLN B2B
• Your code will power mission-critical systems used by financial professionals and institutions across the US and globally.

What This Job Offers

• Job Type: Full-time
• Career Level: Senior
• Education Level: No Education Listed