Rainer Bieniek - Senior Developer

Q: Where is Rainer based?

Rainer is based in Großheide, Germany .

Q: What languages does Rainer speak?

Rainer speaks the following languages: German (Native), English (Advanced) .

Q: How many years of experience does Rainer have?

Rainer has at least 33 years of experience. During this time, Rainer has worked in at least 16 different roles and for 18 different companies . The average length of individual experience is 2 years and 6 months . Note that Rainer may not have shared all experience and actually has more experience.

Q: What is Rainer's latest experience?

Rainer's most recent position is Senior Developer at RWE Trading .

Q: What companies has Rainer worked for in recent years?

In recent years, Rainer has worked for RWE Trading , Hagebau IT , Open Source Office , Airrplus , and Signal Iduna .

Q: Which industries is Rainer most experienced in?

Rainer is most experienced in industries like Telecommunication , Information Technology (IT) , and Transportation and Logistics . Rainer also has some experience in Insurance , Government and Public Administration , and Energy .

Q: Which business areas is Rainer most experienced in?

Rainer is most experienced in business areas like Information Technology (IT) , Product Development , and Operations . Rainer also has some experience in Customer Service , Business Intelligence , and Project Management .

Q: Which industries has Rainer worked in recently?

Rainer has recently worked in industries like Information Technology (IT) , Insurance , and Energy .

Q: Which business areas has Rainer worked in recently?

Rainer has recently worked in business areas like Information Technology (IT) , Product Development , and Operations .

Recommended expert

Großheide, Germany

Experience

Feb 2025 - Jul 2025

6 months

Senior Developer

RWE Trading

Developed custom microservices for power exchanges based on Spring Boot 3 using PostgreSQL, ActiveMQ, Kafka, and S3
Refactored and reimplemented legacy microservices (Scala / Akka) on Spring Boot 3
DevOps tasks for operating microservices in an AWS runtime environment
Senior role in development in collaboration with an internal client

Jul 2023 - Mar 2025

1 year 9 months

Senior Developer

Hagebau IT

Lead developer for building custom microservices in the data pool area based on Spring Boot 3 using MongoDB, Elasticsearch, and Kafka
DevOps tasks for running microservices in a HashiCorp Nomad runtime environment
Direct support for project management

Jul 2021 - Jul 2024

3 years 1 month

Senior Lead Developer (Part-time)

Open Source Office

Further developed the Open Source Review Toolkit in the area of FOSS compliance
Integrated the microservice architecture with OAuth2 / OpenID systems and set up the Keycloak system
Lead developer for custom microservices to automate FOSS compliance processes on Spring Boot 2 & 3
Configured, managed, and administered the AWS runtime environment
Senior role in DevOps and development tasks in collaboration with an internal client

Jul 2021 - Mar 2023

1 year 9 months

Senior Lead Developer

Airrplus

Integrated the microservice architecture with OAuth2 / OpenID systems and extended Keycloak with custom modules
Operational support for Red Hat SSO / Keycloak
Lead developer for custom microservices in authentication, authorization, and CRM integration on Spring Boot 2 & 3
DevOps tasks for running microservices in a Microsoft Azure runtime environment

Nov 2019 - Jun 2021

1 year 8 months

Senior Development Lead

Signal Iduna

Technical lead of the internal developer team for cloud-based services in the electronic document archive
Designed and implemented a microservice architecture for archiving and validating PDF documents (PDF/A)
Integrated with existing OAuth2 / OpenID systems
Planned and implemented operational and technical metrics in the microservice architecture
Established and executed a DevOps approach in development and operations

Oct 2018 - Oct 2019

1 year 1 month

System Architecture Consultant

ITZ Bund

Support in the area of system architecture for the implementation of a register-based process
Creating concepts and building a proof of concept for an on-premises private cloud infrastructure
Troubleshooting and evaluating concepts and processes in collaboration with the internal client

Sep 2018 - Sep 2018

1 month

Developer

Kühne & Nagel

Development of RESTful microservices and GWT web applications in air freight logistics
Using Java 8, Java EE 7, Spring Framework, and messaging architectures (SOA, REST, EIP)
Designing mobile and desktop-based dialogs using HTML5

Jul 2018 - Aug 2018

2 months

System Architecture Consultant

ITZBund

Support in the area of system architecture for the implementation of a register-based process
Detecting, analyzing, and resolving errors in application and infrastructure components
Containerization and Docker deployment

Apr 2018 - Aug 2018

5 months

Solution Designer

Vodafone Group

Designing and implementing a solution for scheduled invocation of REST service endpoints (up to one hundred parallel calls/second)
Using Spring Boot, Akka Messaging, Quartz, Infinispan, Docker, and Kubernetes

Apr 2017 - Jun 2018

1 year 3 months

Solution Architect & Lead Developer

Hermes Deutschland

Designing and implementing a microservice architecture for backend and middleware services (order creation for private customers)
Introducing Akka Messaging, Infinispan Data Grid, and Kafka
Migrating from Spring Boot 1 to Spring Boot 2, using Docker, Kubernetes, OpenStack, and OpenShift
Building a CI/CD platform with Jenkins and implementing a DevOps process

Jan 2017 - Mar 2017

3 months

Developer

Deutsche Bahn

Set up a logging solution for a project replacing handhelds with Android tablets
Developed a RESTful microservice to store and retrieve logs
Integrated a search engine implementation into a relational database

Nov 2016 - Dec 2016

2 months

Architecture Consultant

Mobilcom / Debitel

Advised on architecture and design to build an internal API for document and print services
Analyzed and gave recommendations based on Domain-Driven Design
Designed and implemented a RESTful web service for the Apigee Edge Gateway

Oct 2016 - Oct 2016

1 month

Developer

Vodafone Group Services

Developed API proxies to migrate SOAP endpoints to REST using Spring Framework, Spring Boot, and Spring Cloud
Designed a global OAuth2/OpenID infrastructure and integrated it into the API gateway

Jan 2016 - Dec 2016

1 year

Developer

Kühne+Nagel

Developed RESTful microservices and GWT web applications in air freight logistics
Built programmable mock implementations for REST and SOAP services
On-demand PDF generation with Apache FOP and XSL-FO, virtualization using VirtualBox and Docker

Aug 2015 - Nov 2015

4 months

Developer

Hydro Aluminium Rolled Products

Developed a solution for managing the storage area with Java 7, JSF, EJB, JPA, and Wildfly 8.2
Developed and tested business logic, PC and mobile dialogs, and integration tests with external systems

Jan 2011 - Dec 2015

5 years

Technical Lead & Lead Architect

Vodafone Group Services

Technical Lead & Lead Architect for the APIX API Exposure Gateway for controlled backend integration
API/RESTful/Microservice design and NoSQL (Cassandra) schema design
Migration of SOAP interfaces to RESTful services (HATEOAS)
Support for IoT prototypes (MQTT) and distributed log collector solutions on Kafka

Jan 2008 - Dec 2011

4 years

Technical Lead

Vodafone Group Services

Architecture and implementation of a chat bridge solution between Vodafone 360 and chat networks (Google Talk, Yahoo, MSN)
Team lead for developing scalable Hadoop-based reporting solutions for data volumes up to 1 TB/month

Jan 2006 - Dec 2008

3 years

JEE Developer

Vodafone Group Services

JEE development for the customer self-service portal and migration of the billing system to ESB/Tibco
Design and implementation of the MMS product D2 Easy Reply

Jan 2006 - Dec 2008

3 years

Prototype Developer

Vodafone Group Services

Prototype development and field trial live@home (Mobile World Congress 2007)
Group SMS solution GroupComms and integration into networks
Planning and operation of development and test environments

Jan 1992 - Dec 1996

5 years

Managing Partner, Technology

GTN – Society for Telecommunications and Network Services

Planning, setup, and operation of the first private nationwide German internet data network with international connections
Organization and management of first and second level support

Jan 1988 - Dec 1993

6 years

Consultant

GTT – Company for Telephone and Telecommunications Consulting

Planning, building and operating in-house data networks
Developing custom software solutions for telephone and data networks

Jan 1983 - Dec 1988

6 years

Freelancer

Independent Software Developer

Designing and implementing computer games for Sinclair ZX Spectrum, QL and Commodore Amiga
Developing hardware and drivers for sound solutions and hard disk drives

Industries Experience

See where this freelancer has spent most of their professional time. Longer bars indicate deeper hands-on experience, while shorter ones reflect targeted or project-based work.

Experienced in Telecommunication (19.5 years), Information Technology (9.5 years), Transportation (2.5 years), Insurance (1.5 years), Government and Administration (1 year), and Energy (0.5 years).

Telecommunication

Information Technology

Transportation

Insurance

Government and Administration

Energy

Business Areas Experience

The graph below provides a cumulative view of the freelancer's experience across multiple business areas, calculated from completed and active engagements. It highlights the areas where the freelancer has most frequently contributed to planning, execution, and delivery of business outcomes.

Experienced in Information Technology (33.5 years), Product Development (17.5 years), Operations (8 years), Customer Service (5 years), Business Intelligence (4 years), and Project Management (1.5 years).

Information Technology

Product Development

Operations

Customer Service

Business Intelligence

Project Management

Summary

Programming languages: Java, C, C++, C#, Rust, Shell, Perl, Sed, Awk
IDEs: IntelliJ, Eclipse, Visual Studio, Xcode
Tools: Maven, Gradle, Git, Ant, Subversion, RCS, CVS
Test & integration frameworks: JUnit 4/5, Mockito, AssertJ, Awaitility, TDD, BDD, Jenkins
Web design: Bootstrap, Tailwind CSS / UI
Frameworks: Spring Boot / Framework (WebMVC, Reactive) / Data / Cloud / Security, OSGi, Apache Camel, Swing, JEE & WildFly / JBoss, Apache Hadoop, Hibernate
Operating systems: Solaris / Linux / FreeBSD, Windows
Databases: PostgreSQL, MySQL, Oracle, Sybase, MS-SQL, MongoDB, Cassandra, Redis, Memcached
Process models: Scrum, Kanban, V-Model, Waterfall model
Project experience in Domain-Driven Design

Languages

German

Native

English

Advanced

Profile

Created

September 2025

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Frequently asked questions

Do you have questions? Here you can find further information.

Where is Rainer based?

Rainer is based in Großheide, Germany.

What languages does Rainer speak?

Rainer speaks the following languages: German (Native), English (Advanced).

How many years of experience does Rainer have?

Rainer has at least 33 years of experience. During this time, Rainer has worked in at least 16 different roles and for 18 different companies. The average length of individual experience is 2 years and 6 months. Note that Rainer may not have shared all experience and actually has more experience.

What roles would Rainer be best suited for?

Based on recent experience, Rainer would be well-suited for roles such as: Senior Developer, Senior Lead Developer (Part-time), Senior Lead Developer.

What is Rainer's latest experience?

Rainer's most recent position is Senior Developer at RWE Trading.

What companies has Rainer worked for in recent years?

In recent years, Rainer has worked for RWE Trading, Hagebau IT, Open Source Office, Airrplus, and Signal Iduna.

Which industries is Rainer most experienced in?

Rainer is most experienced in industries like Telecommunication, Information Technology (IT), and Transportation and Logistics. Rainer also has some experience in Insurance, Government and Public Administration, and Energy.

Which business areas is Rainer most experienced in?

Rainer is most experienced in business areas like Information Technology (IT), Product Development, and Operations. Rainer also has some experience in Customer Service, Business Intelligence, and Project Management.

Which industries has Rainer worked in recently?

Rainer has recently worked in industries like Information Technology (IT), Insurance, and Energy.

Which business areas has Rainer worked in recently?

Rainer has recently worked in business areas like Information Technology (IT), Product Development, and Operations.

What is the availability of Rainer?

Rainer is immediately available for suitable projects.

What is the rate of Rainer?

Rainer's rate depends on the specific project requirements. Please use the Meet button on the profile to schedule a meeting and discuss the details.