Marcus Biel-Java Cloud Expert
Check rate
Experience
Java and Quarkus Expert
Large German energy service provider
- Modernization of a large-scale Java enterprise application*
The project is modernizing a complex enterprise application that has grown over many years. The existing Spring-based legacy system runs on Java 8, OSGi, and Eclipse RCP and is being gradually migrated to a modern, maintainable architecture with Java 25 and Quarkus.
Marcus works on analysis, architecture, refactoring, and implementation. One focus is on untangling historically grown structures and dependencies and on building a clean, sustainable Java and Quarkus technology stack.
Tools & technologies: Java 8, Java 25, Quarkus, Hibernate ORM with Panache, EclipseLink, OSGi, Eclipse RCP, Maven, JUnit, Mockito, REST, JSON, Git, Eclipse IDE, IntelliJ IDEA Ultimate, Jira, Confluence
Java Cloud Expert
Unknown
- Modernized and modularized a legacy monolith to enable independent team workflows
- Migrated from Java 8 to Java 21 and from Spring Boot 2 to Spring Boot 3.3
- Simplified Maven project structure, reducing build time from 15 minutes to 50 seconds
- Converting architecture to a hexagonal DDD architecture with end-to-end integration tests using RestAssured and JUnit 5
- Tools and technologies: Java 8-22, Spring Boot, Mockito, AssertJ, RestAssured, Hibernate, OracleDB, Flyway, REST, JSON, Docker, Kubernetes, AWS, Bitbucket, GitHub, SonarQube, IntelliJ IDEA Ultimate
Software Engineer
Unknown
- Designed, architected, implemented and tested a SaaS solution for a medium-sized customer in the financial sector
- Tools and technologies: Java 11, Quarkus, Stripe, PDFBox, JUnit 5, Mockito, AssertJ, Hibernate, PostgreSQL, Flyway, REST, JSON, Docker, GitLab, SonarQube, IntelliJ IDEA Ultimate; Java 8, Java 11, Spring Boot, Kafka, JUnit 5, Mockito, AssertJ, JPA, H2, Microsoft SQL Server, Liquibase, REST, JSON, Lombok, Docker, Kubernetes, Jenkins, Git on Bitbucket, SonarQube, IntelliJ IDEA Ultimate
Integration Engineer
Unknown
- Designed, implemented, tested and maintained Spring Boot based microservices for credit card system integration of a large German financial institution in the UK market
- Processed, validated and handled events in a Kafka-based high-concurrency system on Azure Cloud
- Tools and technologies: Java 8, Java 11, Spring Boot, Kafka, JUnit 5, Mockito, AssertJ, JPA, H2, Microsoft SQL Server, Liquibase, REST, JSON, Lombok, Docker, Kubernetes, Jenkins, Git on Bitbucket, SonarQube, IntelliJ IDEA Ultimate
Integration Architect
Unknown
- Designed and architected a Spring Boot based microservice architecture for automated GwG-compliant identity verification
- Integrated a remote provider for secure creation of electronic signatures (QES)
- Tools and technologies: Java 8, Java 11, Spring Boot, JUnit 4, Mockito, AssertJ, JPA, H2, PostgreSQL, Flyway, REST, JSON, Lombok, Docker, Kubernetes, Jenkins, Git on GitHub, SonarQube, IntelliJ IDEA Ultimate
Lead Developer
maildroppa.com
- Led a remote team of software developers, designers and technical writers to develop an email marketing automation SaaS tool
- Tools and technologies:
- Backend: Java 22, Quarkus, JUnit 5, Hibernate Panache, JAX-RS, RESTEasy, JSON, Jackson, Auth0, JWT/OAuth 2.0, Flyway, PDFBox, Stripe, Docker, DigitalOcean Cloud, GitLab, SonarCloud, IntelliJ IDEA Ultimate, Postman
- Frontend App: React 18.x with React Router and React Hooks
- Sales page: Fully responsive HTML5, Figma
- SEO: Ahrefs, Semrush, Tagparrot, Google Search Console, NeuronWriter, Contentpace, Google Analytics, Plausible, Online Outreach
Full Stack Developer
Unknown
- Greenfield development of an online tool for visualization of healthcare insurance data with Angular frontend and Java 11 backend
- Supported architecture design, implementation and testing of Java microservices with JUnit 5 and end-to-end REST interface testing with Postman
- Tools and technologies: Java 11, Micronaut, JUnit 5, Mockito, AssertJ, JPA, H2, PostgreSQL, Flyway, REST, JSON, Lombok, Logback, Docker, Kubernetes, Jenkins, Git on GitHub, SonarQube, IntelliJ IDEA Ultimate, Postman
Principal Product Manager Technical
Red Hat GmbH
- Created vision for Red Hat's tools and technology and inspired professional software and systems engineers
- Led Developer Experience strategies across multiple product teams
- Responsibilities:
- Creating technical content
- Speaking at conferences
- Empowering engineers by delivering hands-on workshops
- Building partnerships with individuals, companies and organizations
- Connecting with other engineers to identify how Red Hat can help them succeed
- Gathering product feedback to inform engineering decisions
- Supporting engineers on forums, social media, meet-ups and other channels
SOA Specialist
Vodafone Kabel Deutschland GmbH
- Designed, developed, tested and maintained distributed large-scale resilient systems
- Focus on backend/middleware development of SOA web services and batch jobs
- Tools and technologies: Java 8, Spring 4, Spring Batch, JPA 2.1, Mockito, PowerMock, JUnit, Maven, SonarQube
Software Architect
financial.com AG
- Implemented load-balanced JBoss domain clustering for full-time availability and system resilience
- Tools and technologies: JBoss AS 7.1, Apache 2.2, ModCluster 1.2, Linux, MySQL 5, Maven 3.0.4, Hudson 2.x, Nexus 2.x
Senior Software Engineer
Wirecard AG
- Processed NFC and credit card transactions in real time and in batch with high performance and reliability
- Developed REST and SOAP based B2B and B2C communication and web frontend extensions
- Defined design, architecture, and implementation guidelines for the development team
- Conducted interviews and acted as the interface to product management
- Tools and technologies: Java SE 6 & 7, Java EE 5, Spring 3.1, Hibernate 3.6, Tapestry 4, SOA (REST, SOAP), Maven 3.0.4, Jenkins 1.5, Nexus, Sonar Server, Oracle 11, Tomcat 7, Jetty 8/9, Eclipse 4.2, Linux
Senior Software Developer
abs Fondsplattform
- Developed UI for a SOAP-based stock market ordering proxy
- Introduced quality guidelines with Sonar Server and managed release and production rollout on a Tomcat cluster
- Tools and technologies: Java SE 5 & 6, Java EE 5, Spring, Hibernate, Cocoon, SOA (XML, SOAP, Hessian), Liquibase, Maven 2+3, Hudson, Nexus, Sonar Server, Eclipse 3.5, Oracle 10, Tomcat 6, Linux
Frontend Developer
Searchteq
- Led SEO and XML local search interface used by Bing Maps, increasing unique visitors tenfold
- Converted development projects from Maven 1 to Maven 2 and provided in-house training
- Integrated Hudson and Nexus for the CI environment
- Frontend development with Java, HTML, CSS, AJAX for local search engine
- Tools and technologies: Java SE 5 & 6, Java EE 5, Spring, Hibernate, SOA (XML, JSON), SEO, JSP + JSTL 1.1, Apache POI, HTML, CSS, JavaScript, AJAX, Maven 1+2, Hudson, Nexus, Tomcat, Linux
Frontend Developer
NCR AG
- Designed and implemented a retail cash management application in a store environment using Java Swing and JGoodies Forms Framework
- Tools and technologies: Java SE 5, Swing, JGoodies Framework, SQL, MS SQL, Tomcat 5.5, Eclipse 3.2
Frontend Developer (Working Student)
Innowake GmbH
- Extended a PHP-based image database and XML parser
- Developed an interface for a barcode scanner
- Tools and technologies: Java SE 5, J2EE 1.4, Struts 1.2, PHP 4, XML, Maven 1, Apache, Tomcat 5.5, DB2, Eclipse 3.1
Frontend Developer (Internship)
Digicon Ltd.
- Refactored a Java CMS and implemented JUnit tests
- Created acceptance tests with FitNesse and performed SEO optimization of a website
- Tools and technologies: Java SE 1.4, J2EE 1.4, Servlets, JSP, SEO, Fit+FitNesse, JBoss, Eclipse 2.1
Frontend Developer (Internship)
Site Ezy Ltd.
- Implemented a PHP SMS module and developed VB.NET user interfaces with database access
- Designed databases for MySQL and MS SQL Server
- Tools and technologies: PHP 4, VB.NET, SQL, MySQL, MS SQL Server, Visual Studio, Dreamweaver
Frontend Developer (Internship)
BMW AG
- Developed a Struts-based user interface for querying an Oracle database of BMW vehicle parts
- Tools and technologies: Java SE 1.4, J2EE 1.3, Struts 1.02, Tomcat 4.1, JDBC, SQL, Oracle, Eclipse 2.0
Intern
PC Professional Magazine
- Worked as a technical editor, participated in editorial meetings and researched magazine articles
- Composed news flashes and performed hardware benchmarking
Industry experience
See where this freelancer has spent most of their professional time.
Experienced in Information Technology, Banking and Finance, Telecommunication, Energy, Healthcare, and Insurance.
Business area experience
See which departments and functions this freelancer has contributed to most.
Experienced in Information Technology, Product Development, Marketing, Quality Assurance, and Strategy.
Summary
Marcus is a Java architect, SaaS founder, and hands-on product developer with 25 years of Java experience. He combines deep enterprise experience with real end-to-end product development - from modernizing grown legacy systems and high-performance event-driven architectures to cloud-native platforms based on Java 26.
Since 2020, he has been designing, building, and running Maildroppa, a cloud-native multi-tenant SaaS platform for email marketing. His responsibility covers the full product lifecycle: requirements engineering, product and UX design, architecture, Java and React development, AI integration, security, networks and firewalls, Docker and containerized deployments, cloud infrastructure, CI/CD, billing, operations, and production support.
In client projects, Marcus modernizes complex Java systems and builds maintainable, business-critical software. He works with modular monoliths and microservices, Spring Boot, Quarkus, Kafka, Docker, Kubernetes, and cloud platforms. The focus is on clear business boundaries, automated tests, performance, security, and reliable operations.
In addition, Marcus has been active in the international Java community for many years. He was an elected member of the JCP Executive Committee, was named Developer Champion by Oracle, spoke at international conferences, and contributed as a technical reviewer to several well-known Java books.
Skills
Java & Frameworks Java 1.3 – Java 26, Java Se, Java Me, Java Ee/J2ee, Jakarta Ee, Quarkus 3, Spring Boot, Spring Framework, Spring Batch, Hibernate Orm, Hibernate Orm With Panache, Eclipselink, Micronaut, Jpa, Hql, Jpql, Cdi, Jms, Jta, Jaxb, Jax-Rs, Resteasy, Java Reflection, Jdbc, Servlets, Jsp, Jstl
Architecture & Integration Software Architecture, Cloud-Native Architecture, Domain-Driven Design (Ddd), Hexagonal Architecture, Modular Monolith, Microservices, Event-Driven Architecture, Distributed Systems, Saas, Multi-Tenant Architecture, Soa, Rest Apis, Soap, Webservices, Kafka, Batch Processing, B2b-/B2c-Integration, High-Concurrency Systems
Software Engineering & Development Practices Clean Code, Test-Driven Development (Tdd), Software Craftsmanship, Requirements Engineering, Technical Leadership, Legacy Modernization, Backend Development, Middleware Development
Build, Testing & Code Quality Maven, Junit 3/4/5, Testng, Mockito, Assertj, Rest Assured, Archunit, Powermock, Fit, Fitnesse, Unit Tests, Integration Tests, End-To-End Tests, Test Coverage, Static Code Analysis, Sonarqube, Sonarcloud, Sonar Server, Postman
Databases & Persistence Mariadb 11.X, Postgresql, Oracle Database, Microsoft Sql Server, Mysql, H2, Db2, Sql, Flyway, Liquibase
Cloud, Containers, Infrastructure & Operations Docker, Kubernetes, Hetzner Cloud, Digitalocean Cloud, Aws, Aws S3, Microsoft Azure, Cloudflare, Linux, Ubuntu, Cloud Server Administration, Server Provisioning, Ssh, Systemd, Networking, Tcp/Ip, Dns, Proxying, Cdn, Waf, Ipv4/Ipv6, Firewalls, Ufw, Security Hardening, Tls/Ssl, Https, Let'S Encrypt, Caddy, Reverse Proxy, Load Balancing, Clustering, Failover, High Availability, Scalability, Performance Optimization, Monitoring, Logging, Backup & Restore, Deployment, Production Operations, Production Support
Ci/Cd & Version Control Git, Github, Gitlab, Bitbucket, Ci/Cd, Jenkins, Gitlab Ci/Cd, Github Actions, Github Workflows, Hudson, Nexus, Release Management, Build Optimization
Security & Identity Oauth 2.0, Jwt, Auth0, Identity Verification, Qualified Electronic Signatures (Qes)
Application Server & Enterprise Java Oracle Weblogic Server, Jboss As, Jboss Domain Clustering, Apache Http Server, Mod Cluster, Tomcat, Tomcat Clustering, Jetty, Osgi, Eclipse Rcp
Frontend & Design React 19, React Router, React Hooks, Angular, Javascript, Html5, Css, Ajax, Java Swing, Jgoodies Forms, Figma
Ai Openai Api, Retrieval-Augmented Generation (Rag)
Libraries & Data Formats Jackson, Json, Xml, Lombok, Logback, Apache Pdfbox, Apache Poi, Hessian
Development & Project Tools Intellij Idea Ultimate, Eclipse Ide, Jira, Confluence
Product Development Ux, Billing, Subscription Billing, Stripe
Seo & Analytics Seo, Analytics, Web Analytics, Google Analytics, Google Search Console, Plausible, Ahrefs, Semrush, Tagparrot, Neuronwriter, Contentpace, Online Outreach
Legacy Web Frameworks Struts, Tapestry, Cocoon
Languages
Education
University of Applied Sciences Augsburg
Computer Science Degree · Computer Science · Augsburg, Germany · 1,3
Certifications & licenses
Scrum Alliance
Scrum Alliance
Statistics
Experience
Global experience
Expertise
Qualifications
Profile
Frequently asked questions
Have questions? Find more information here.
Marcus is based in Grünwald, Germany and can operate in on-site, hybrid, and remote work models.
Marcus speaks the following languages: German (Native), English (Advanced), Spanish (Intermediate).
Marcus has at least 21 years of experience. During this time, Marcus has worked in at least 16 different roles and for 15 different companies. The average length of individual experience is 1 year and 1 month. Note that Marcus may not have shared all experience and actually has more experience.
Based on recent experience, Marcus would be well-suited for roles such as: Java and Quarkus Expert, Java Cloud Expert, Software Engineer.
Marcus's most recent position is Java and Quarkus Expert at Large German energy service provider.
In recent years, Marcus has worked for Large German energy service provider, Unknown, and maildroppa.com.
Marcus is most experienced in industries like Information Technology, Banking and Finance, and Telecommunication. Marcus also has some experience in Energy, Healthcare, and Insurance.
Marcus is most experienced in business areas like Information Technology, Product Development, and Marketing. Marcus also has some experience in Quality Assurance, Strategy, and Research and Development.
Marcus has recently worked in industries like Information Technology, Banking and Finance, and Energy.
Marcus has recently worked in business areas like Information Technology, Product Development, and Marketing.
Marcus holds a Master in Computer Science from University of Applied Sciences Augsburg.
Marcus has 2 certificates. These include: Certified Scrum Master and Certified Scrum Product Owner.
Marcus is immediately available full-time for suitable projects.
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The median daily rate is the middle value of all daily rates — half of comparable freelancers charge less, half charge more. Unlike the average, it is barely affected by outliers.
Calculated based on our freelancers’ daily rates as of 7 Sep 2026. Actual rates may vary depending on seniority level, experience, skill specialization, project complexity, and engagement length.
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