Maciej Rosiek, Software Developer in Berlin, Germany
Maciej Rosiek

Software Developer in Berlin, Germany

Member since November 28, 2015
Maciej is a full-stack software engineer currently living and working in Berlin. He has successfully created highly distributed systems using Java EE (Spring, JPA, Hibernate), as well as JavaScript and Node.js (Express, Loopback), along with front ends using JavaScript and AngularJS, React, or React Native.
Maciej is now available for hire




Berlin, Germany



Preferred Environment

Git, IntelliJ IDEA, Linux

The most amazing...

...application I've created is an event processing bus providing near real-time rule-based product information.


  • Full-stack Software Developer

    2016 - PRESENT
    WeltN24 - Axel Springer
    • Supported development of social features for
    • Designed and created a database and API for the comments system.
    • Architected and developed performant and lightweight UI.
    Technologies: Amazon Web Services (AWS), AWS, MongoDB, Java, Scala, React
  • Full-stack Developer

    2016 - 2016
    Refined Edge Solutions (
    • Owned the existing back-end created using Node.js and Loopback.
    • Migrated the application to another AWS region.
    • Introduced a continuous delivery pipeline using Docker and Elastic Beanstalk.
    • Optimized performance of database queries.
    • Created a new iOS application using React Native.
    Technologies: Amazon Web Services (AWS), AWS, React Native, PostgreSQL, Loopback, Node.js
  • Lead Developer/Tech Lead

    2012 - 2016
    • Managed the back-end development team.
    • Spearheaded the design and architecture of the system.
    • Liaised between programmers and management.
    • Took ownership of product delivery.
    • Mentored junior team members.
    • Recruited developers.
    • Developed a distributed eCommerce back-end system with asynchronous event processing, microservices with AWS and Docker, and REST and SOAP APIs.
    • Created front-ends for internal usage development using AngularJS or React.js (Redux) including E2E testing using Protractor and Selenium running on Node.js.
    • Built a messaging bus appliance using HornetQ with monitoring and metrics.
    • Developed a highly scalable distributed event processing component to aggregate product data using Vertx and Kotlin.
    Technologies: Redux, React, Node.js, AngularJS, JavaScript, Python, Scala, Vert.x, Kotlin, Solr, CXF, PostgreSQL, Spring, Java
  • Java EE Developer

    2011 - 2012
    On Demand
    • Developed a back-end system for video streaming (VOD).
    • Created new file storage for multimedia data for HLS (HTTP Live Streaming).
    • Supported the maintenance of a CRM using Ruby On Rails.
    • Conducted functional and integration testing using JUnit.
    • Facilitated performance testing using JMeter.
    • Migrated from JBoss 4.2 to JBoss 5.1.
    Technologies: Hibernate, Spring, JPA, CXF, JSF, EJB 3, JBoss, Java
  • Java Web Developer

    2010 - 2011
    Crystal Brains
    • Developed web applications running on Google App Engine.
    • Created an e-learning platform using Ext JS framework.
    Technologies: Git, Maven, Ext JS, JavaScript, Java
  • Java Web Developer

    2008 - 2011
    InsERT S.A.
    • Developed a web application based on Apache Cocoon Framework.
    • Integrated Hippo CMS with existing document repository to provide a complete solution.
    • Migrated Castor JDO to JPA implementation using Hibernate.
    • Migrated Castor XML to JAXB implementation.
    • Created Axis Soap web services.
    • Created and maintained the application front-end using HTML, CSS, and JavaScript (jQuery).
    Technologies: Castor EDC, XSLT, XML, Axis, Apache Lucene, Hibernate, Spring, Apache Tomcat, Java
  • Java Web Developer

    2007 - 2007
    • Developed web application Oversee to monitor telecommunication nodes.
    • Migrated the application from Java version 1.4 to 5.
    • Created web services to exchange data between front-end and back-end components.
    Technologies: Subversion (SVN), Servlet, JSP, Apache Struts, Enterprise Java Beans (EJB), JBoss, Jakarta EE, Java


  • Product Repository

    Big Data product repository as a core component for storing and manipulating product data of one of the biggest eCommerce fashion retailers in Europe. I was the lead developer responsible for designing the API and architecting the components. It was developed using Java, Spring, CXF and PostgreSQL.

  • Messaging Application

    An embedded HornetQ package, deployable as web application with monitoring and metrics. I was a main developer, responsible for core development and maintenance. This appliance is used as a main event bus for Zalando because of its reliability and availability. I used HornetQ, Java, and Rest APIs to complete this project.

  • Startup Weekend Fashion & Tech Poznan

    I was invited as a mentor to a Fashion & Technology startup competition in Poznan. My role was to help develop business ideas revolving around technology and fashion. I'm proud I could help young entrepreneurs to realize their dream ideas.


  • Languages

    SQL, Kotlin, Java, JavaScript, XSLT, CSS, HTML, Groovy, HTML5, XML, Python, Scala
  • Frameworks

    JPA, Vert.x, JUnit, Apache CXF, Hibernate, Spring MVC, Spring, AngularJS, Spring Boot, Grails, React Native, Redux, CXF, JSF, Ext JS, Apache Struts, JSP, Loopback
  • Tools

    Maven, Git, Apache JMeter, Apache Solr, Gradle, IntelliJ IDEA, Solr, Apache Tomcat, Servlet, Subversion (SVN)
  • Paradigms

    Agile Software Development, Unit Testing, Test-driven Development (TDD), Testing, Functional Programming, Reactive Programming
  • Storage

    PostgreSQL, JSON, Spring Data, NoSQL, AWS DynamoDB, MongoDB, MySQL
  • Other

    Freelance, EJB 3, AWS, Enterprise Java Beans (EJB)
  • Libraries/APIs

    Apache Lucene, Node.js, React, Axis, Cocoon
  • Platforms

    Amazon Web Services (AWS), Docker, JBoss, Linux, Castor EDC, Jakarta EE


  • Master's degree in Software Engineering
    2004 - 2009
    Wroclaw University of Technology - Wroclaw/Poland

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