Senior .NET Fullstack Developer

Optiveum; Warszawa; Remote; PLN 181,000 - 217,000; Full time

Job summary

Optiveum is seeking a Senior .NET Fullstack Developer to join our client team in a 100% remote role. You will work on business-critical full-stack apps, modernizing legacy systems, and building scalable APIs in .NET and Azure.

The role emphasizes ownership, CI/CD with GitHub Actions, strong testing practices, documentation, and collaboration with cross-functional teams. Fluent English is required; Polish-based remote work is supported.

Qualifications

• Senior-level experience in full-stack software development.
• Strong C# and .NET skills for legacy modernization.
• Experience with Azure cloud services and GitHub Actions.
• Knowledge of APIs, architecture, and security best practices.
• Fluent English communication.

Responsibilities

• Develop, maintain, and improve full-stack applications.
• Migrate legacy solutions to current .NET versions.
• Work across UI, backend, APIs, and data sources.
• Design features for research-related entities.
• Establish and improve Azure infrastructure.
• Create and maintain CI/CD pipelines with GitHub Actions.
• Enhance quality via automated tests, reviews, observability, and docs.
• Support applications through lifecycle balancing maintenance and new development.

Skills

Senior-level experience

C# & .NET

Azure

CI/CD (GitHub Actions)

APIs & Architecture

Testing & Observability

Documentation

English fluent

Tools

GitHub Actions

Azure

Job description

Senior .NET Fullstack Developer

About the role:

We are Optiveum, and we are currently looking for a Senior .NET Fullstack Developer to join the team of our client—a global, research-driven organization. In this setup, Optiveum acts as the recruitment and contracting party, meaning you will sign the B2B cooperation agreement directly with us.

Key Details:

• Location: 100% Remote (Based in Poland / Warsaw)

• Rate: Up to 36 EUR/h

• Mode of work: Full-time (40 hours/week)

• Language requirement: English (Fluent)

What you will be doing:

• Developing, maintaining, and improving business-critical full-stack applications.

• Modernizing legacy applications and migrating solutions to current versions of .NET.

• Working seamlessly across all application layers, including UI, backend services, APIs, and data sources.

• Designing and implementing new functionalities that support the registration of new molecules and other research entities.

• Establishing and improving Azure infrastructure for both modernized and existing applications.

• Creating and maintaining CI/CD pipelines using GitHub Actions.

• Improving engineering quality through automated testing, code reviews, secure development practices, observability, and comprehensive documentation.

• Supporting applications throughout their lifecycle, balancing maintenance, operational stability, technical debt reduction, and new development.

What we are looking for:

• Several years of senior-level professional experience in full-stack software development.

• Strong, hands-on experience with C# and .NET, including maintaining existing solutions and upgrading/migrating legacy applications to newer versions.

• Practical knowledge of Oracle databases, SQL, data access, and integration between applications and database platforms.

• Hands-on experience with Azure cloud services and CI/CD pipelines (preferably GitHub Actions).

• A broad understanding of software architecture, APIs, application security, testing, and deployment.

• A self-driven working style with the confidence to take full ownership of tasks and solutions.

• Fluent English communication skills.

Does this sound like a match? Apply today!