KAROLINA ROZYCKA
Houten
Summary
Senior Software Engineer – Backend Focus, with deep expertise in Java, Spring Boot, Hibernate, and Kotlin, building scalable, production-grade systems since 2018. I specialize in clean architecture, high-performance services, and long-term maintainability, with a strong focus on solving complex technical challenges and delivering robust backend solutions.
Overview
7
7
years of professional experience
Work History
Senior Software Engineer
Stadtraum GmbH
02.2024 - Current
- Leading backend development for smart mobility and parking infrastructure across Germany and Poland, supporting hospitals, airports, supermarkets, shopping malls, and private parking facilities
- Refactored legacy Jakarta EE / GlassFish and PHP-based systems into modular Spring Boot/Kotlin microservices, following clean architecture principles to improve scalability and maintainability
- Designed and deployed an embedded control system on Raspberry Pi, managing real-time communication with sensors, cameras, gates, traffic lights, ticket machines, and display systems
- Built a cloud-based backend platform to manage diverse parking hardware and edge devices, ensuring seamless integration and centralized control
- Delivered secure RESTful APIs using Spring Security, Hibernate, PostgreSQL, and Flyway, with authentication managed via Keycloak
- Integrated with the SCS platform to handle real-time data via WebSockets, TCP, and HTTP endpoints from physical infrastructure
- Designed and developed backend systems for mobile applications, enabling advance parking reservations and city-level platform integrations
- Supported on-street public parking services through backend integration with external apps such as Mobilet
- Managed deployments on Linux-based virtual machines, collaborating closely with DevOps on infrastructure, monitoring, and security
- Utilized GitLab CI/CD, Docker, JUnit, Swagger, Maven, Grafana, and Prometheus in a fully automated, observable, and agile development environment
- Mentored junior developers, contributed to system architecture, and supported the transition to a microservice-oriented ecosystem
Senior Software Engineer
Humanoo eTherapists GmbH
09.2022 - 01.2024
- Designed and maintained Java/Spring Boot microservices using MySQL, Redis, and AWS services, scaling the platform from a single mobile app to multiple product lines
- Led the refactoring of a monolithic architecture into modular microservices, enhancing scalability, maintainability, and deployment efficiency
- Built and documented REST APIs, integrated with Amazon S3, EC2, and implemented monitoring using CloudWatch and New Relic
- Developed key backend features, including a personalized recommendation engine, challenge and reward systems, and activity data processing (e.g. steps, workouts), enabling adaptive and engaging user experiences
- Contributed to frontend development using TypeScript and Angular for internal admin tools and select customer-facing components
- Participated in architectural planning, service decomposition, and performance optimization to support a growing multi-app ecosystem
- Mentored junior developers, led code reviews, and supported onboarding within agile, cross-functional squads
- Worked with Docker, GitHub, CircleCI, SonarQube, JUnit, Maven, and Jira in a CI/CD and TDD-driven environment
Software Engineer
Humanoo eTherapists GmbH
04.2020 - 09.2022
Junior Software Engineer
Humanoo eTherapists GmbH
06.2018 - 04.2020
Education
Bachelor - Computer Science and Engineering
University of Warmia And Mazury in Olsztyn
04.2018
Skills
Languages:
- Java
- SQL (PostgreSQL / MySQL)
- Kotlin
- Python
- C#
- C
- TypeScript
Technologies:
- Spring Boot / Spring Framework
- REST APIs / RESTful APIs
- Hibernate / JPA
- Microservices / Microservice Architecture
- Testing (JUnit, TDD)
- Clean Code & Refactoring
- Legacy System Migration
- Maven
- Git
- OAuth2 / OpenID Connect
- Event-Driven Architecture
- Agile / Scrum
- Docker
- CI/CD (GitLab)
- Linux Server Management
- Flyway / Liquibase
- AWS (Lambda, EC2, S3, RDS, SQS, SNS)
- WebSockets
- Jakarta EE
- Redis
- Domain-Driven Design (DDD)
- Cloud (AWS or Linux VMs)
- Keycloak
- Swagger / OpenAPI
Languages
English
Bilingual or Proficient (C2)
Polish
Bilingual or Proficient (C2)
German
Elementary (A2)
Timeline
Senior Software Engineer
Stadtraum GmbH
02.2024 - Current
Senior Software Engineer
Humanoo eTherapists GmbH
09.2022 - 01.2024
Software Engineer
Humanoo eTherapists GmbH
04.2020 - 09.2022
Junior Software Engineer
Humanoo eTherapists GmbH
06.2018 - 04.2020
Bachelor - Computer Science and Engineering
University of Warmia And Mazury in Olsztyn
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