Senior .NET/React developer - Leiden

As a Senior .NET/React Developer, you will join an innovative fintech company that develops advanced investment solutions within the digital assets market. Using its proprietary platform, the company automates complex trading processes and analyzes large volumes of data to support intelligent investment strategies. All software is developed entirely in-house, making technology a core part of the business.

The company is currently in an exciting scale-up phase and has a team of approximately 15 employees. The IT department consists of a compact Scrum team responsible for the entire technical landscape. Team members are encouraged to take ownership, contribute ideas, and influence technical decisions. Developers work closely with colleagues from both the trading and business teams, allowing ideas to be translated into practical solutions quickly.

The company culture is informal, ambitious, and results-driven. Employees work primarily from the office (four days per week), fostering close collaboration. The team enjoys lunch together every day, and regular social events and team activities are organized.

Functie

As a Senior Full-Stack Developer, you will play a key role in developing a modern software platform within an innovative fintech environment. You will be responsible for designing, building, and optimizing business-critical applications while helping shape the platform’s technical direction.

The primary focus is on back-end development within the Microsoft Azure ecosystem, using .NET, C#, and API integrations. You’ll also have the opportunity to contribute to the front-end, working with React and TypeScript.

Because of the company’s small and agile structure, you’ll have significant responsibility and be involved throughout the entire software development lifecycle—from architecture and implementation to deployment and maintenance. You’ll share your expertise with colleagues, conduct code reviews, and help maintain high development standards across the team.

Your Responsibilities:

• Design, develop, and enhance applications within the Microsoft Azure platform.
• Build reliable back-end services, REST APIs, and integrations with external systems.
• Develop modern web applications using .NET, C#, React, and TypeScript.
• Make architectural and technical decisions for new features and enhancements.
• Design, optimize, and maintain databases and data models.
• Ensure software quality, performance, security, and scalability.
• Improve CI/CD pipelines and contribute to DevOps best practices.
• Conduct code reviews and mentor colleagues on technical challenges.

Functie-eisen

• Bachelor’s degree or equivalent level of thinking and working (HBO level).
• At least 5 years of professional software development experience.
• Strong experience with .NET, C#, Microsoft Azure, JavaScript, TypeScript, and at least one modern front-end framework (preferably React).
• Experience with PostgreSQL (or SQL databases) and RESTful APIs.
• A proactive, independent developer with strong analytical and problem-solving skills.

Aanbod

• Competitive salary between €5,000 and €7,000 gross per month.
• Flexible working week of 32, 36, or 40 hours.
• 25 vacation days.
• Travel allowance or full public transport reimbursement.
• Company laptop.
• Mobile phone allowance.
• Hybrid working (up to 1 day per week from home).
• Complimentary catered lunch every day at the office.
• Plenty of room for initiative, ownership, and technical influence.
• Direct impact on products that are used every day.
• An informal working environment with short communication lines and an ambitious team.
• Excellent accessibility by both car and public transport.