Vjeran Marcinko, Developer in Osijek, Croatia
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Vjeran Marcinko

Verified Expert  in Engineering

Domain-driven Design (DDD) Developer

Osijek, Croatia
Toptal Member Since
January 4, 2014

Vjeran is a Java architect and developer working only remotely from home for almost 20 years. He boasts extensive experience designing and implementing complex systems, mostly server-side. He has expert knowledge of domain modeling and object-oriented architectures and loves learning new technologies.


Java, Spring, Gradle, Apache Maven, OAuth 2, SQL, Amazon Web Services (AWS)...
Kapsch Carrier Com Croatia
MyBatis, RabbitMQ, ActiveMQ, Axis, SOAP, Quartz, Apache Velocity...
XML-RPC, J2ME, Servlet, NIO, Apache, Applets, Java, Back-end, XML




Preferred Environment

Gradle, Git, IntelliJ IDEA, Linux

The most amazing...

...thing I've ever created is a generic adapter for communication with any remote device connected to the M2M platform.

Work Experience

Senior Java Developer | Architect

2018 - PRESENT
  • Architected and developed an application that aims to provide end-users capabilities to manage insurance contracts, contract memberships as well as integrate those capabilities with existing enterprise systems.
  • Helped development of eCommerce platform as an architect-consultant and a senior software engineer, taking on integration tasks and helping other members of the team.
  • Involved in big enterprise application as an architect and a senior software engineer to deliver solutions for a big construction company's internal needs – various business processes, service integration, and reporting.
Technologies: Java, Spring, Gradle, Apache Maven, OAuth 2, SQL, Amazon Web Services (AWS), Microservices, Angular, JPA, PostgreSQL, Spring Boot, MySQL, Back-end, Functional Programming, Git, SOAP, XML, Hibernate

Senior Java Developer | Architect

2004 - 2018
Kapsch Carrier Com Croatia
  • Created an over-the-air configurator for delivery of configuration profiles to mobile handsets, such as ones for configuring GPRS/CSD connection, a WAP browser, e-mail settings. Worked in a team of two as project leader, architect, and developer.
  • Created the web administration console for a message gateway server in a completely remote capacity. Used the Jakarta Tapestry web framework for presentation and the Apache Axis library for SOAP communication.
  • Upgraded a platform for mass SMS distribution. Provided complex hierarchical organization of entities and a statistical overview. Used Spring for the business layer, Jakarta Turbine for web, Torque as an O/R layer, and Quartz for scheduling.
  • Created an MGW client library, a user-friendly layer built on top of ParlayX web service stubs, for sending and receiving SMS/MMS/WAP Push SI messages. Used the Apache Axis and JDOM libraries.
  • Architected a number portability central database platform for a Croatian telecommunication agency. Utilized JBoss AS and Spring (business logic), Jakarta Tapestry (web), iText (PDF reporting), and Apache Axis (web services).
  • Created a transaction server acting as a user-friendly gateway for prepaid/postpaid billing. Implemented on-request or subscription-based charging. Apache Tapestry, Spring, Quartz, and plain JDBC/SQL as a persistence layer.
  • Created a web console as well as some core platform functionality for managing various services related to roaming subscribers. Used Apache Tapestry, Spring, Quartz, and plain JDBC/SQL as the persistence layer.
  • Developed a platform for managing business processes for Value Added Services in Telco companies. Used Spring, Quartz, Hibernate, Tapestry.
  • Architected the majority of the core functionality for a Machine-to-Machine (M2M) platform operating as a Big Data system for collecting and processing data from remote devices in the field.
Technologies: MyBatis, RabbitMQ, ActiveMQ, Axis, SOAP, Quartz, Apache Velocity, Apache Turbine, Hadoop, Neo4j, Cassandra, Tapestry, Hibernate, Spring, Java, JPA, PostgreSQL, Spring Boot, MySQL, Back-end, Apache Kafka, Functional Programming, Cascading, Clojure, XML

Java Developer

2001 - 2004
  • Created a chat system consisting of client applets and a Java server based on Jakarta Avalon technology. Integrated a virtual call center platform. Consisted of a Java 1.1 user applet for WAN usage and a Java 1.4+ applet for administrators inside the application's LAN.
  • Created a firewall tunneling solution for Java using periodic HTTP POST requests to simulate constant socket connection. Wrote the client side consisting of a thin client library, usable on the Java 1.1+ platform. Wrote the server side implemented by Java Servlet technology. Utilized event-based (NIO) networking for high performance on the server side.
  • Created a J2ME/MIDP client application for the unified messaging platform, communicating through the XML-RPC interface.
  • Developed an auto-generator of a custom expression language manual from custom tags in source files.
  • Handled load testing of a unified messaging platform using Jakarta JMeter with custom developed samplers. Simulated hundreds of simultaneous clients.
Technologies: XML-RPC, J2ME, Servlet, NIO, Apache, Applets, Java, Back-end, XML

Phone Number Manager Implementation

I have contributed to numerous large-scale projects, one of which involved the implementation of a phone number manager. In this project, I focused on crafting service layer beans that easily adhere to their designated interfaces.

The phone number manager was designed for a platform responsible for managing mobile numbers as they are ported between various operators. By implementing a range of Java-based actions specifically tailored to handle phone numbers, the service layer bean effectively facilitates the critical processes necessary to transfer mobile numbers across different telecommunications providers seamlessly.
1995 - 2001

Master's Degree in Electronical Engineering

Faculty of Electronical Engineering - Osijek, Croatia


MyBatis, Quartz, Axis


Servlet, IntelliJ IDEA, Apache, ActiveMQ, RabbitMQ, Git, Gradle, Apache Maven


JPA, Spring Boot, Hibernate, Tapestry, Spring, JUnit, Apache Velocity, OAuth 2, Netty, TestNG, Hadoop, Angular


Java, XML, SQL, HTML, JavaScript, Clojure


J2ME, Amazon Web Services (AWS), Apache Kafka, Linux


Functional Programming, Object-oriented Programming (OOP), Test-driven Development (TDD), Microservices


HSQL, Neo4j, XML-RPC, PostgreSQL, MySQL, H2, Cassandra


Back-end, Architecture, APIs, SOAP, Domain-driven Design (DDD), Applets, NIO, Apache Turbine, Cascading

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