Jens O.-Freelance Java Developer / DevOps Engineer
Check rate
Experience
Freelance Java Developer / DevOps Engineer
Unpublished defense company
- Extension of OSGi modules in a complex communication solution
- Debugging communication with Wireshark and remotely in the JENS test environment
- Migration of tests from TestNG to JUnit 5 with Mockito and AssertJ
- Updating vulnerable dependencies and improving code quality
- Changes to the Vaadin frontend
- Increasing test coverage
Freelance Java Developer
Bosch
- Improving data quality of an eMobility platform
- Analyzing data in MongoDB and various cleanups with Python scripts
- Adjustments and optimizations to several microservices for data processing
- Supply chain security and upgrades of dependency and JDK versions
Freelance Java Developer
Zyres
Freelance Java Developer
CrossEngage
Freelance Java Developer
MediaMarktSaturn
- Extension of various microservices and deployment to Google Cloud (GCP)
- Updating Spring Boot and using additional GCP features
- Load testing of a service and optimizations using Redis cache for higher loads
- Introducing tests and code quality in the team
Freelance Java Developer
1&1 Mail & Media Development & Technology GmbH
- Further development of an existing web application in an 8-person Scrum team
- Adaptation of microservices using TDD
- Compliance with high coding standards with support from Sonar
Freelance Java Developer
The unbelievable Machine Company
- Increased the test coverage of an existing web application from 13% to 82%
- Updated dependencies with Maven and OWASP Dependency Checks
Freelance Java Developer
Elinvar GmbH
- Further development of various microservices for data import and processing
- New development of a service for importing and archiving securities documents
- Optimization of the build process with regard to code coverage
- Smooth migration of microservices to the Spring Boot framework
Freelance Java Developer
IT Sonix Custom Development GmbH
- Development of an invoicing system for an energy company in a five-person Scrum team
- Refactoring of the components and extension with new features
- Improvement of automatic quality control
- Documentation of the business logic and protection through corresponding tests
Senior Java Developer / DevOps Engineer
Pamyra GmbH
- Further development of a microservice architecture based on Spring Boot and Kubernetes
- Expansion of logging and monitoring based on the ELK stack
- Introduction of quality control and increase in test coverage
- Refinement of the development process
Senior Java Developer / Project Owner
Kiwigrid GmbH
- Analyzed requirements and worked with stakeholders to define suitable projects
- Evaluated different alerting and stream processing frameworks
- Developed a driver to connect special customer hardware to the Energy Manager
- Set up a cloud instance in Google Public Cloud with Kubernetes
Lead Java Developer
cognitix GmbH
- Led an international team of 4 Java developers
- Developed a system for processing and visualizing information from network traffic
- Prepared, normalized, and aggregated data with Kafka and Apache Flink
- Coordinated with other teams and project management
- Planned and assigned tasks
- Configured the build system, code analysis with SonarQube, and deployment with Docker
Software Developer / DevOps Engineer
tarent solutions GmbH
- Worked on a legacy web application based on Velocity with Lucene backend and Oracle database
- Standardized the code style and revised the release cycle
- Supported crisis situations through log file and performance analysis
- Extended a Spring MVC web application and further developed the VerA.Web product
- Revised deployment with Docker and Ansible
- Worked on the company-wide build and Maven repository infrastructure
- DevOps in the Telekom Internet of Things project with deployment, monitoring, load and performance tests
- Contributed to the open source and software quality focus areas
Software Developer
Aperto AG
- Developed CMS (Magnolia) projects in an agile team of 7
- Adapted a Maven archetype, improved the build process, and implemented Selenium tests
Software Developer
Pinguin AG
- Worked in a Scrum team of 5 with PO and designer
- Developed an Android app with Maven, Android Annotations, and ActionBar Sherlock
- Implemented the REST backend in Glassfish with Spring and Jersey
- Created OSGi server modules with Spring and Hibernate
- Installed and connected a search and logging server with ElasticSearch and Graylog2
- Test-driven development and pair programming
- Installed and operated the build system (Jenkins, Nexus, Sonar, Git)
- Worked with a team in Thailand through training, code reviews, and interface delivery
Software Developer
Prodato Integration Technologie GmbH
- Refactoring and cleaning up a process management software and presenting it to the customer
- Migrating projects to Maven
- Co-developing a JSF interface for an Oracle data warehouse
- Short assignment in the SAP BW and BSP area at Siemens Healthcare
Software Developer in the Development & Research department
Keynote Sigos GmbH
- Co-developing a Swing interface as well as analyzing and fixing errors
- Connecting a map interface in the project team
- Migrating the backend from TCL web server to Tomcat servlet with XML protocol implementation
- Introducing tests with JUnit and an automated build system
- Switching the build tool from Ant to Maven and the code repositories to Git
Working student and internship in Support and the IS&T department
SUSE Linux GmbH
- Linux support and server administration
- PHP development with MySQL database
- Support with administration of the PKI infrastructure
Industry experience
See where this freelancer has spent most of their professional time.
Experienced in Information Technology, Professional Services, Automotive, Energy, Aerospace and Defense, and Retail.
Business area experience
See which departments and functions this freelancer has contributed to most.
Experienced in Information Technology, Product Development, Customer Service, Quality Assurance, Operations, and Research and Development.
Skills
Java
Maven
Linux Administration
Spring Boot
Html & Css
Jenkins
Continious Integration
Git
Junit 5
Mockito
Assertj
Lombok
Sonarqube
Test Driven Development
Mysql
Logging Log4j2,Slf4j
Shell Script
Ansible
Jenkins Pipeline
Github Actions
Gitlab Ci
Gradle
Google Public Cloud
Kibana
Docker
Jira/Confluence
Python
Arduino And Microcontrollers
Rabbitmq
Mongodb
Elasticsearch
Kafka
Kubernetes
Openapi
Postgresql
Javascript
Apache Flink
Selenium
Vaadin
Very Good Java Knowledge
Very Good Linux Knowledge
Continious Integration With Github Actions, Jenkins Or Gitlab Ci
Devops With Ansible, Docker, Kubernetes And Cloud (Gcp And Aws)
Database Knowledge (Especially Mysql And Postgresql)
Geographic Information Systems (Gis)
Driver Programming
Logging And Monitoring
Test-Driven Development
Software Quality Assurance With Sonar, Owasp And Other Tools
Languages
Education
Georg-Simon-Ohm-Fachhochschule
Diploma in Computer Science (University of Applied Sciences) · Computer Science · Nuremberg, Germany
Friedrich-Alexander-Universität Erlangen-Nürnberg
Diploma in Computer Science (not completed) · Computer Science · Erlangen, Germany
Student exchange
Melbourne, Australia
Certifications & licenses
Java Web Hacking & Hardening
Maven
Novell Certified Linux Administrator
VHS course: Linux on the network
Statistics
Experience
Global experience
Expertise
Qualifications
Profile
Frequently asked questions
Have questions? Find more information here.
Jens is based in Leipzig, Germany and can operate in on-site, hybrid, and remote work models.
Jens speaks the following languages: German (Native), English (Intermediate).
Jens has at least 22 years of experience. During this time, Jens has worked in at least 9 different roles and for 18 different companies. The average length of individual experience is 1 year and 3 months. Note that Jens may not have shared all experience and actually has more experience.
Based on recent experience, Jens would be well-suited for roles such as: Freelance Java Developer / DevOps Engineer, Freelance Java Developer, Senior Java Developer / DevOps Engineer.
Jens's most recent position is Freelance Java Developer / DevOps Engineer at Unpublished defense company.
In recent years, Jens has worked for Unpublished defense company, Bosch, Zyres, CrossEngage, and MediaMarktSaturn.
Jens is most experienced in industries like Information Technology, Professional Services, and Energy. Jens also has some experience in Automotive, Aerospace and Defense, and Retail.
Jens is most experienced in business areas like Information Technology, Product Development, and Customer Service. Jens also has some experience in Quality Assurance, Operations, and Research and Development.
Jens has recently worked in industries like Automotive, Aerospace and Defense, and Information Technology.
Jens has recently worked in business areas like Information Technology, Quality Assurance, and Product Development.
Jens holds a Doctorate in Computer Science from Friedrich-Alexander-Universität Erlangen-Nürnberg.
Jens has 5 certificates. Among them, these include: Java Web Hacking & Hardening, Maven, and Novell Certified Linux Administrator.
Jens is immediately available full-time for suitable projects.
Daily rate distribution
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Average rates for similar positions
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The average daily rate is the mean of all daily rates from recent contracts of comparable freelancers on our platform.
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 15 Sep 2026. Actual rates may vary depending on seniority level, experience, skill specialization, project complexity, and engagement length.
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