Senior Backend Developer (.NET) – Iot Platform

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 across 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 backend software development experience
• Strong knowledge of C#, .NET 6/7/8+, ASP.NET Core Web API, and Entity Framework Core
• Experience designing RESTful APIs
• Practical knowledge of microservices architecture and distributed systems
• Production experience with PostgreSQL including schema design and query optimization
• Familiarity with message queue systems and asynchronous communication (RabbitMQ or Kafka)
• Experience with Docker and Kubernetes
• Ability to write unit and integration tests using tools like xUnit, NUnit, Moq, FluentAssertions, or Testcontainers
• Knowledge of application security including OAuth2, OpenID Connect, JWT, and identity management systems
• Teamwork and effective communication skills
• Proficiency in English (spoken and written)

Nice to have:

• Experience with IoT platforms and protocols (MQTT, AMQP, Modbus, SNMP, IEC 61850)
• Knowledge of Keycloak
• Experience with ScyllaDB or Cassandra
• Familiarity with Terraform and Helm
• Understanding of PKI and mTLS authentication
• Experience with multi-tenant architecture
• Knowledge of monitoring and observability tools
• Familiarity with Event Sourcing, CQRS, and gRPC communication

• Design and develop scalable microservices using .NET (C#, ASP.NET Core Web API, Entity Framework Core)
• Create and enhance REST APIs for integration with external systems
• Implement multi-tenant architecture with secure data separation and access control
• Develop integration services for Industrial IoT devices handling telemetry and configuration data
• Work with PostgreSQL and NoSQL databases
• Utilize RabbitMQ and Kafka for event-driven architecture
• Apply security best practices including OAuth2, OpenID Connect, JWT, PKI/mTLS, and identity management
• Ensure code quality through unit and integration tests, code reviews, and adherence to SOLID and Clean Code principles
• Collaborate on containerization and deployments in Kubernetes environments
• Develop and maintain CI/CD processes and infrastructure as code using Terraform and Helm
• Optimize system performance for handling thousands of devices and large data volumes
• Work closely with product teams, architects, and DevOps engineers