Senior Fullstack Developer (.NET / React)

j-labs is a Polish software company founded in 2010, specializing in software development with expertise in Java, JavaScript, .NET, Kotlin, Python, QA, and DevOps. The company operates in three locations: Cracow, Warsaw, and Munich, serving over 75 clients in fintech, telco, e-commerce, travel & airlines, automotive, logistics, and banking sectors. It employs over 500 engineers with an average experience of 11 years, focusing on microservice and DLT centers of excellence including consulting, training, and software development.

• Minimum 6 years of .NET development experience.
• Practical experience with React and TypeScript.
• Experience designing systems from scratch (greenfield).
• Strong system design skills.
• Very good knowledge of PostgreSQL.
• Experience with integrations and data-heavy systems.
• Experience working with Azure or other cloud solutions.
• Experience with CI/CD and automation.
• Ability to work under pressure and deliver solutions.
• Proactive problem-solving attitude.
• Openness to working with AI and practical use of AI tools in daily development (commercial experience not required).
• Very good command of Polish and English (minimum B2).

Nice to have:

• Experience in financial systems.
• Experience with AI agents.
• Experience in tech leadership.
• Knowledge of Snowflake / data layer.
• Experience with AI workflows.
• Experience with SQL Server (legacy).

• Design microservice architecture for a greenfield financial system.
• Develop software using .NET (70%) and React (30%).
• Create integrations with external systems and internal modules.
• Build and maintain CI/CD processes and automate deployments.
• Co-define software development lifecycle including release strategy, testing, and rollout.
• Implement AI tools in the development process such as coding, refactoring, and testing.