Contributed to the modernization and maintenance of a long-standing enterprise system with dual architecture tracks: a legacy Java EE platform (v1) and a partially modernized Java Spring-based system (v2). The product operated in a regulated, highly formalized environment with a strong emphasis on architectural consistency and review processes.

Key Responsibilities & Contributions:

• Worked on both backend and frontend parts across two versions of the platform: – v1: Legacy Java EE application (circa 2006) with XML-based configuration, ServiceFinder, Sybase ACE 16 DB, and FreeMarker-like templating engine. – v2: Java 8 monolith using Spring (without Boot) and AngularJS, where most business logic was implemented in stored procedures.
• Improved performance of critical data-heavy views by introducing custom pagination in Sybase (despite internal belief that it was impossible). Reduced query response times from 40 seconds to under 1 second.
• Optimized existing logic and database procedures; most work focused on refactoring and improving legacy code stability rather than new features.
• Participated in highly formal architectural review processes, aligning changes with internal technical guidelines and standards.

Technologies & Tools: Java EE, Java 8, Spring (non-Boot), AngularJS, JavaScript, JDBC, Sybase ACE 16, XML, ServiceFinder, FreeMarker.

Worked on a chatbot-focused project implemented in Kotlin using a reactive microservices architecture based on Vert.x. The project involved both backend and frontend development.

Key Responsibilities & Contributions:

• Developed new features and resolved bugs across the stack.
• Built and maintained a custom integration testing framework to ensure end-to-end stability.
• Worked with the Angular 7 frontend to implement UI features based on wireframes and project requirements.
• Participated in code reviews and contributed to codebase refactoring and optimization.
• Ensured high code quality and emphasized reusability and maintainability.

Technologies & Tools: Kotlin (JDK 11), Vert.x, MongoDB, JUnit, Angular 7.

Worked on a B2B travel platform that enabled merchants to process payments using a wide range of methods including credit cards, cryptocurrency, and payment links. The system followed a microservices architecture with high scalability and resilience requirements.

Key Responsibilities & Achievements:

• Designed and implemented business workflows using Camunda BPMN, integrating them into distributed microservices.
• Developed and maintained Java/Kotlin-based microservices, following clean architecture principles.
• Led the decoupling of a monolithic Java application into several independent, containerized microservices.
• Integrated the system with multiple payment gateways, ensuring secure and fault-tolerant processing.
• Adopted Kotlin in 2020 for new services to accelerate development and improve maintainability.
• Built services to work with Amazon S3 for file storage and integrated components with AWS services.
• Deployed services using Docker and Kubernetes, ensuring smooth CI/CD pipelines.
• Utilized Kafka and Redis for asynchronous communication and caching between services.
• Wrote robust unit and integration tests, ensuring high test coverage and production readiness.

Technologies & Tools: Java (JDK 11), Kotlin, Spring Boot, Hibernate, PostgreSQL, Docker, Kubernetes, Apache Kafka, Redis, Amazon S3, AWS, Camunda BPMN.

Key Responsibilities & Achievements:

• Designed and developed an internal MVP platform for HR use that aggregated job candidates from multiple sources — external APIs, uploaded Excel (XLS) files, and internal databases — with automatic deduplication and filtering logic.
• Streamlined the hiring workflow by creating a centralized system for managing and reviewing candidate data, improving recruiter efficiency and decision-making speed.
• Implemented logic for dynamic Excel file parsing and data import, ensuring flexibility for non-technical users.
• Refactored and optimized legacy code, improving performance and maintainability.
• Wrote robust unit and integration tests (JUnit) to ensure stability during active development.
• Maintained and improved an existing legacy AngularJS project.
• Started gaining practical experience with GraphQL for API development.

Tech Stack: Java (Spring Boot), React, Angular / AngularJS, REST APIs, GraphQL (intro), Excel parsing (Apache POI), MySQL / PostgreSQL, JUnit, Git