About Krzysztof
I am a Senior Java & Full-Stack Software Engineer with 12+ years of experience building production software for enterprise, fintech, retail/e-commerce, IoT and ERP environments.
I help companies design, build and modernize backend services, web applications, APIs, integrations and business-critical systems. My core stack includes Java, Spring Boot, TypeScript, Angular, React.js, Node.js, PostgreSQL, DB2, Kafka, Docker and Kubernetes.
I have worked on long-term B2B and product projects for companies such as REWE Digital Poland, BIOT, Cinkciarz.pl and TRAX, covering domains like retail, e-commerce, foreign exchange, IoT, logistics and business process automation.
I am especially useful when a project needs a hands-on senior engineer who can understand business requirements, work with legacy and modern systems, improve code quality, deliver production-ready features and communicate clearly in remote teams.
Polish
Native or bilingual
English
Fluent
Remote only
Primarily works remotely
Experience
- Krzysztof Janiec kjaniec.devSenior Full-Stack Software EngineerDIGITAL AND ITJuly 2019 - Today (6 years and 11 months)Zielona Góra, Poland
- Senior Software Engineer working as a B2B contractor with 12+ years of experience in full-stack development, backend architecture and production systems.
- Delivered software for clients and companies across e-commerce, IoT, fintech, ERP, finance, logistics and supply chain domains.
- Built and maintained backend services, APIs, integrations and business-critical applications using Java, Spring Boot, TypeScript, Node.js, PostgreSQL, DB2, Kafka, RabbitMQ and Docker/Kubernetes.
- Developed modern web applications, admin panels and data-driven interfaces with React, Angular, Material UI, Mapbox/Deck.gl and related frontend technologies.
- Took ownership of technical design, implementation, code quality, performance improvements, remote collaboration and end-to-end delivery in long-term B2B projects.
- REWE Digital PolandSenior Java & Full-Stack Software EngineerRETAIL (LARGE RETAILERS)July 2024 - Today (1 year and 11 months)Zielona Góra, Poland
- B2B Senior Software Engineer working on enterprise retail and e-commerce systems for REWE Digital Poland
- Developing and maintaining backend and frontend features using Java, Spring Boot, TypeScript and Angular.
- Working on integrations and business workflows connected with enterprise legacy systems, including COBOL-based components.
- Building and improving APIs, distributed application components and production services used in large-scale retail environments.
- Working with Java, Spring Boot, Angular, TypeScript, DB2, Kafka, Keycloak, Docker, Kubernetes and legacy enterprise systems.
- Contributing to technical analysis, implementation planning, code quality, refactoring and modernization of business-critical software.
- BIOT Sp. z o.o.Full-Stack Software EngineerINTERNET OF THINGS (IOT)July 2019 - June 2024 (4 years and 11 months)Zielona Góra, Poland
- Worked as a B2B Full-Stack Software Engineer on IoT, microservices and data-driven web applications.
- Designed, developed and maintained microservices, APIs and real-time system components using TypeScript, Node.js, PostgreSQL, RabbitMQ, gRPC and GraphQL.
- Built modern frontend applications, dashboards and operational interfaces with React, MobX, Material UI, Mapbox and Deck.gl.
- Implemented integrations, data visualization features, geospatial interfaces and backend workflows for connected-device and monitoring systems.
- Worked with technologies such as TypeScript, Node.js, React, PostgreSQL, TypeORM, RabbitMQ, gRPC, GraphQL, Elasticsearch, Mapbox and Deck.gl.
- Took ownership of feature delivery, technical analysis, code quality, debugging, performance improvements and long-term maintenance.
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Education
- Master's DegreeUniversity of Zielona Góra2014Master’s degree studies focused on computer science, software engineering and practical software development. Relevant areas include programming, databases, web applications, system design and engineering practices.