Jens Oberender - Freelance Java Developer / DevOps Engineer

Leipzig, Germany

Experience

Jun 2024 - Mar 2025

10 months

Remote

Freelance Java Developer / DevOps Engineer

Undisclosed defense company

Expansion of OSGi modules in a complex communication solution
Debugging communication with Wireshark and remotely in the JENS test environment
Migrating tests from TestNG to JUnit5 with Mockito and AssertJ
Updating vulnerable dependencies and improving code quality
Changes to the Vaadin front end
Increasing test coverage
GitLab CI
OSGi
Karaf
Maven
SonarQube
Mockito
JUnit5
AssertJ
Code quality
OpenAPI
Lombok
Wireshark
Vaadin

Sep 2022 - Apr 2024

1 year 8 months

Leipzig, Germany

Freelance Java Developer

Bosch

Improving data quality of an eMobility platform
Analyzing data in MongoDB and performing various cleanups, partly with Python scripts
Adjustments and optimizations to multiple microservices for data processing
Supply chain security, upgrading dependencies and JDK versions
Spring Boot
Jenkins
MongoDB
Maven
RabbitMQ
SonarQube
Nexus IQ
Mockito
JUnit5
Code quality
Python
Docker
Vulnerability scans
Dependency Check/Tracker
Kubernetes
AWS
SBOM

Jun 2022 - Nov 2022

6 months

Freelance Java Developer

Zyres

Advising on architecture topics for a new project
Adjusting GitLab CI in conjunction with Qodana
Optimizing stream processing from RabbitMQ
Spring Boot
GitLab CI
Qodana
Gradle
RabbitMQ
JUnit5
Mockito

Mar 2022 - Aug 2022

6 months

Freelance Java Developer

CrossEngage

Upgrading a monolith to Java 11 and newer dependency versions
Extending a microservice based on Micronaut
Code reviews in a cross-functional team (8 members)
Performance analysis and optimization proposals
Spring
JUnit5
Mockito
Maven
Gradle
Jenkins
Bitbucket
Micronaut
Tomcat
Apache Avro
gRPC

Jul 2021 - Feb 2022

8 months

Freelance Java Developer

MediaMarktSaturn

Extending various microservices and deploying to Google Cloud (GCP)
Updating Spring Boot and using additional GCP features
Load testing a service and optimizing with Redis cache for higher loads
Introducing tests and code quality practices to the team
Spring Boot
JUnit5
TDD
Mockito
Maven
GCP
Pub/Sub
GitHub
OWASP Dependency Check
Kafka
SonarQube
Code quality
Jira

Apr 2021 - Jun 2021

3 months

Freelance Java Developer

1&1 Mail & Media Development & Technology GmbH

Enhancing an existing web application within an 8-member Scrum team
Modifying microservices using TDD
Maintaining high coding standards with Sonar support
Spring Boot
JUnit5
TDD
Mockito
Maven
Tomcat
GitLab
Jenkins
Jira

Feb 2021 - Apr 2021

3 months

Freelance Java Developer

The unbelievable Machine Company

Increasing test coverage of an existing web application from 13% to 82%
Updating dependencies using Maven and OWASP Dependency Check
Spring Boot
JUnit5
TDD
Mockito
Maven
GitLab CI
OWASP Dependency Check
Jira

Aug 2020 - Jan 2021

6 months

Freelance Java Developer

Elinvar GmbH

Developing various microservices for data import and processing
Creating a new service for importing and archiving securities documents
Optimizing the build process for better code coverage
Gradual migration of microservices to the Spring Boot framework
Spring Boot
Gradle
JUnit5
TDD
Kubernetes
Kafka
GitLab CI
Kibana
Docker
Git
Jira
Confluence

Feb 2020 - Jul 2020

6 months

Remote

Freelance Java Developer

IT Sonix Custom Development GmbH

Project to develop a billing system for an energy company
Mostly remote work in a five-member Scrum team
Refactoring components and adding new features
Improving automated quality control
Documenting business logic and securing it with appropriate tests
Spring Boot
Maven
JUnit5
TDD
GitLab CI
Kibana
Azure Service Bus
Docker
OWASP Dependency Check
SpotBugs
Git
Jira
Confluence

Aug 2019 - Nov 2019

4 months

Senior Java Developer / DevOps Engineer

Pamyra GmbH

Evolving a microservice architecture based on Spring Boot and Kubernetes
Expanding logging and monitoring using the ELK stack
Implementing quality control and increasing test coverage
Refining the development process
Spring Boot
Maven
MySQL
Kafka
JUnit5
TDD
Jenkins
Kibana
GitLab
SonarQube
Docker
Kubernetes
JPA
Git

May 2018 - Aug 2019

1 year 4 months

Senior Java Developer / Project Owner

Kiwigrid GmbH

Analyzing various requirements and drafting projects with stakeholders
Evaluating different alerting and stream-processing frameworks for the projects
Developing a driver to connect special customer hardware to Kiwigrid’s Energy Manager
Setting up a cloud instance in Google Public Cloud using Kubernetes
PlantUML
OpenAPI
Lombok
Maven
Jenkins
GitLab
SonarQube
Kubernetes
Git
Jira
Confluence

Sep 2017 - Apr 2018

8 months

Lead Java Developer

cognitix GmbH

Leading an international team of 4 Java developers, one of whom works from home four days a week
Developing a system to process and visualize network traffic data
Preparing, normalizing, and aggregating data with Kafka and Apache Flink
Coordinating with other teams and project management
Planning and distributing tasks
Configuring the build system, code analysis with SonarQube, and deployment with Docker
Spring Boot
Apache Flink
OpenAPI
Lombok
Maven
GitLab CI
SonarQube
Elasticsearch
Kibana
Kafka
Docker Compose
Git

Feb 2015 - Aug 2017

2 years 7 months

Software Developer / DevOps Engineer

tarent solutions GmbH

Working on a legacy web application based on Velocity with a Lucene backend and Oracle database
Unifying code style; code analysis with Sonar, PMD, Checkstyle; revising the release cycle
Crisis support in another project through log file and performance analysis
Extending a Spring MVC web application
Developing the VerA.Web product and managing the build system
Revising deployment with Docker and Ansible
Contributing to the overhaul of the company’s build and Maven repository infrastructure
DevOps in a telecom IoT project, handling deployment, monitoring, load and performance tests, error analysis, coordination with customers and vendors
Working on open source and software quality focus areas
Nexus
Maven
PostgreSQL
Ansible
Docker
Jenkins
Shell
Oracle DB
Scrum
Software quality
SonarQube
Selenium
Monitoring
Git
Jira

Oct 2014 - Dec 2015

3 months

Software Developer

Aperto AG

Developing CMS (Magnolia) projects in a 7-member agile team
Adjusting a Maven archetype, improving the build process, and implementing Selenium tests
Maven
Magnolia
Bamboo
Selenium

Sep 2011 - Sep 2014

3 years 1 month

Software Developer

Pinguin AG

Working in a 5-member Scrum team with a PO and initially a designer
Developing an Android app using Maven, Android Annotations, ActionBar Sherlock, and delivering four white-label versions of the app
Implementing the REST backend on a GlassFish application server with Spring and Jersey
Creating OSGi server modules as a mediation layer between web services, the DB2 database, and other services using Spring and Hibernate
Installing and connecting a search and logging server based on Elasticsearch (Lucene) and Graylog2
Extensive TDD (JUnit, Mockito) and pair programming
Setting up and operating the build system (Jenkins, Nexus, Sonar, Git), supporting administrators
Collaborating with a team in Thailand through training, code reviews, API provisioning, and design discussions
Scrum
Maven
Jenkins
Elasticsearch
TDD
Spring
DB2
OSGi
Hibernate
JSF
Android
Monitoring
Logging
Git
Jira

May 2010 - Sep 2011

1 year 5 months

Software Developer

Prodato Integration Technologie GmbH

Refactoring and cleaning up a process management software from a student project to a finished product, and presenting it to the client
Migrating projects to Maven
Co-developing a JSF interface for an Oracle data warehouse
Short assignment in SAP BW and BSP at Siemens Healthcare
Maven
Oracle DW
JSF
RDF
Git

Sep 2007 - Apr 2010

2 years 8 months

Software Developer in Development & Research

Keynote Sigos GmbH

Co-developing a Swing GUI, analyzing and fixing bugs
Software developer in a project team integrating a map interface
Migrating the backend from a TCL web server to a Tomcat servlet, converting and reimplementing parts of the XML protocol with unit tests to ensure integrity
Introducing tests with JUnit, an automated build system, test coverage reporting, migrating build tools from Ant to Maven and code repositories to Git
Swing
Tomcat
GIS
MySQL
Shell
Maven
JUnit
Git
Ant