Thomas Jarnot - Backend Developer, DevOps Engineer

Q: Where is Thomas based?

Thomas is based in Bonn, Germany and can operate in on-site , hybrid , and remote work models.

Q: What languages does Thomas speak?

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

Q: How many years of experience does Thomas have?

Thomas has at least 27 years of experience. During this time, Thomas has worked in at least 18 different roles and for 21 different companies . The average length of individual experience is 1 year and 2 months . Note that Thomas may not have shared all experience and actually has more experience.

Q: What is Thomas's latest experience?

Thomas's most recent position is Backend Developer, DevOps Engineer at AXA Digital Experience .

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

In recent years, Thomas has worked for AXA Digital Experience , REWE digital , Mesalvo , ALD Automotive , and REWE Systems .

Q: Which industries is Thomas most experienced in?

Thomas is most experienced in industries like Professional Services , Banking and Finance , and Retail . Thomas also has some experience in Information Technology , Automotive , and Insurance .

Q: Which business areas is Thomas most experienced in?

Thomas is most experienced in business areas like Information Technology , Product Development , and Quality Assurance . Thomas also has some experience in Customer Service and Business Intelligence .

Q: Which industries has Thomas worked in recently?

Thomas has recently worked in industries like Professional Services , Retail , and Information Technology .

Q: Which business areas has Thomas worked in recently?

Thomas has recently worked in business areas like Information Technology , Product Development , and Quality Assurance .

Recommended expert

Bonn, Germany

Check rate

Experience

May 2024 - Jun 2025

1 year 2 months

Cologne, Germany

Backend Developer, DevOps Engineer

AXA Digital Experience

Further development, modularization, and technical modernization of the My AXA customer portal using Scrum.
Connection of new REST APIs to expand the digital product and service portfolio.
Splitting a monolithic application into clearly defined business responsibilities.
Continuous refactoring of complex code parts to improve maintainability.
Supporting other teams with interface design and introducing WireMock for integration tests.
Standardizing caching and resilience by introducing Spring Cache and Resilience4J.
Cleaning up request validation according to JSR-170 and developing a simulation process.
Further development of the code generator to transform OpenAPI contracts into client libraries.
Development of dashboards and log file analyses using Loki and Grafana Cloud.
Monitoring and reporting of production and QA systems.
Tech stack: Java 21, Spring Boot 3, REST, Resilience4J, Docker, OpenAPI, Grafana Cloud, Jenkins, Tekton, OpenShift, AWS, GitLab.

Aug 2023 - Apr 2024

9 months

Cologne, Germany

Solution Architect, Developer

REWE digital

Worked on the major retail project REWE Bonus to build an in-house customer loyalty solution.
Analysis of historical data models and legacy backends in the area of promotion planning and discount maintenance.
Identification of responsibilities outside the product scope and development of cleaned-up data structures.
Transformation of a COBOL-based record type interface (SEDAS) into a hierarchical domain model.
Design and implementation of the message model for promotional items based on Java and Spock.
Development of an efficient topic design for a Kafka-based message architecture.
Implementation of Kafka producers/consumers based on Kotlin, Quarkus, and Spring Boot.
Consulting on cloud-native, microservice, and data mesh architectures.
Documentation of architecture decisions and promotion of a ubiquitous language.
Tech stack: Java, Kotlin, Spring Boot, Quarkus, Apache Kafka, Docker, REST, GitLab, Spock, IBM DB2, Data Mesh, DDD.

Feb 2023 - Jul 2023

6 months

Freiburg im Breisgau, Germany

Software Developer, Coach

Mesalvo

Improved the codebase in terms of maintainability, test coverage, and modularization for digital medication management.
Built a Docker stack to support local development against MS SQL Server, SAP MaxDB, and MariaDB.
Migrated the monolithic codebase from Java 8 to Java 17.
Identified module boundaries and turned them into a model project based on Spring Boot 3 and REST (Level 3).
Developed and test-driven documented the REST API with Spring REST Docs.
Coached the team on Spring, REST, Docker, and testing strategies (Spock, BDD).
Set up the Azure deployment pipeline and implemented the Azure security concept.
Analyzed and optimized native Linux scripts by moving them into Docker-in-Docker stacks.
Tech stack: Java 17, Groovy, Spring Boot 3, REST, WebFlux, Spock, Hibernate, Liquibase, Docker, Azure Cloud.

Jul 2022 - Dec 2022

6 months

Hamburg, Germany

Architect, Developer, Analyst

ALD Automotive

Greenfield project to digitize and automate customer processes such as vehicle retrieval and contract reclassification.
Analyzed processes using Domain Story Telling and identified stakeholders.
Developed the REST API for customer services with Spring Boot and Kotlin.
Built the public customer frontend with React and TypeScript.
Developed a reactive client library based on Spring WebClient with automatic token refresh.
AWS Kubernetes management via SSH tunneling through Linux bastion hosts.
Set up the Azure deployment pipeline and implemented the security concept.
Connected to Apache Kafka and ran workshops on NATS/JetStream.
Tech stack: Kotlin, Java, Spring Boot, WebFlux, Spock, Docker, Apache Kafka, React, TypeScript, AWS, Kubernetes.

Jan 2021 - Jun 2022

1 year 6 months

Cologne, Germany

Architect, Lead Developer

REWE Systems

Developed the KOS web framework to support the migration of microservices based on Spring Boot.
Designed a platform for digital vouchers with integration of epay and PAYBACK (Kartenwelt project).
Implemented asynchronous processing logic for checkout transactions using REST services and DB2.
Rebuilt Coupon World to provide up to 10 million pre-generated coupons in near real time.
Designed the platform according to Domain-Driven Design principles (generation, redemption, validation, support).
Analysis and risk assessment for the relaunch of the KOS Payback platform toward Google Cloud and Kubernetes.
Designed an event-driven streaming architecture using Apache Kafka.
Introduced Kotlin, Groovy, and Spock (BDD) as well as Docker/Docker Compose in the development team.
Conducted coaching on architecture topics, Domain Story Telling, and clean code principles.
Tech stack: Kotlin, Java, Spring Boot, Apache Kafka, GitLab CI, Docker Compose, DB2, HATEOAS, Testcontainers.

Jul 2020 - Dec 2020

6 months

Berlin, Germany

Software Developer (Fullstack)

DHL IT-Services

Supporting a cross-functional team in the context of a logistics platform.
Automated deletion of personal data in line with GDPR requirements.
Analysis and decommissioning of outdated services and migration into new Kotlin/Spring Boot backends.
Further development of backend services for alternative name spellings and digital copies.
Development of a frontend component based on Vue.js.
Support with incident analysis and technical modernization of legacy systems.
Tech stack: Kotlin, Java, Groovy, Spock, Spring Boot, Vue.js, Maven, Git, Team City, Oracle.

Jan 2019 - Jun 2020

1 year 6 months

Cologne, Germany

Software Developer (Fullstack), Domain Architect

REWE digital

Replacement of the REWE online shop monolith with microservices based on Spring Boot and Kotlin.
Development of services for customer registration, login, and self-services including password reset.
Redesign of a scalable data replication service for message-based synchronization via Kafka.
Implementation of an authorization service based on Spring Security OAuth with Redis integration.
Establishment of clean REST APIs and implementation of a Kotlin DSL for HTTP requests.
Introduction of Kotest (MockK) and aspect-oriented programming to encapsulate technical tasks.
Development of frontend components (BFF) based on Node.js, Next.js, and React.
Implementation of Google reCAPTCHA Enterprise to secure the frontends.
Further development of the monitoring platform using Kibana, Prometheus, and Grafana.
Adaptation of the CI chain to agent-based builds under Jenkins.
Tech stack: Kotlin, Java, Spring Boot, Apache Kafka, PostgreSQL, Docker, Nomad, Consul, Grafana, React, Next.js.

Oct 2018 - Dec 2018

3 months

Cologne, Germany

Software Developer, Technical Coordinator

OBI digital

Responsible for alignment, development, and deployment of the Product Information Service (microservice).
Prototyping of the deployment stack based on Docker (Swarm mode) with Nginx reverse proxy.
Setup of the automated CI chain via Jenkins Declarative Pipeline.
Migration of the deployment stack toward Google Cloud Platform (GKE/Kubernetes).
Establishment of Domain-Driven Design and Consumer-Driven Contract Testing (PACT).
Tracking runtime behavior using Spring Boot Admin.
Tech stack: Spring Boot, REST, Docker, Jenkins, Git, Java, Groovy, Spock, React.

Apr 2018 - Sep 2018

6 months

Technical Lead, Software Developer, DevOps Engineer

ZEG

Architectural realignment of a CMS-based eCommerce platform for specialist retailers.
Driving domain modeling and designing clean RESTful HTTP interfaces.
Implementation of independent microservices for modern orchestration runtimes.
Shift to reactive programming and non-blocking communication.
Externalization of the frontend based on React for better performance.
Increased resilience through sidecar patterns (circuit breaker) and failover strategies.
Setup of monitoring, alerting, and self-healing concepts.
Migration from centralized Bamboo agents to agile builds and infrastructure as code.
Sharing the values of clean code and 12-factor compliance with the team.
Tech stack: Java 8/10, Magnolia CMS, Spring Boot 2, Docker, Kubernetes, GCP, Jenkins, Commercetools.

Jan 2018 - Mar 2018

3 months

Software Developer, Architect

REWE Digital

Development of the Substitute Service for synchronous identification of substitute items in fulfillment centers.
Implementation of a dedicated Elasticsearch cluster for More-Like-This searches.
Setup of a data store consisting of Elasticsearch (items) and JPA/CloudSQL (inventory).
Provision of data by consuming Kafka messages.
Ensuring fault tolerance through the use of Kubernetes and Hystrix (circuit breaker).
Documentation of the web API according to the OpenAPI 3.0 standard using Swagger.
Achieving REST compliance at Maturity Level 3 (HATEOAS).
Tech stack: Spring Boot, Spring Data, Hibernate, Apache Kafka, Elasticsearch, Docker, Kubernetes, Swagger.

Mar 2017 - Dec 2017

10 months

Software Developer, Domain Architect, DevOps Engineer

CBC (Mediengruppe RTL)

Architecture refactoring of an application landscape toward microservices based on Spring Cloud and Docker.
New development of a public REST service to provide program data for network operators.
Implementation of multi-stage security modules as Spring Boot starters for validation and authorization.
Ensuring load balancing and availability using Eureka, Zuul, and Ribbon.
Building the Content Information Service to aggregate metadata based on the Entity-Attribute-Value pattern.
Domain-driven breakdown of the business architecture into scalable bounded contexts.
Migration from standalone Tomcats to Spring Boot and extension of JavaFX clients.
Tech stack: Java, Spring Boot, Spring Cloud, Netflix OSS, Docker, Apache Kafka, RabbitMQ, MSSQL, JavaFX.

Oct 2016 - Feb 2017

5 months

Software Developer, Test Engineer

viaboxx GmbH

Development of the oncology information system NEOdb in a microservice architecture.
Implementation of business modules (Patients, Accounts, Diagnoses, etc.) as bounded contexts.
Implementation of cross-service ID management and a database-per-service approach.
Realization of a filter resolution framework on the REST layer for sorting across modules.
Configuration of SpEL-based rules for thresholds and data types with complex sequencer data.
Connection of KeyCloak for token-based single sign-on.
Provision of the application stack as a Docker runtime for local test scenarios.
Execution of automated integration and UI tests with Cucumber and Selenium.
Compliance with regulatory guidelines such as GAMP (21 CFR Part 11).
Tech stack: Spring Boot, Spring Data, Netflix OSS, Docker, Postgres, PL/pgSQL, KeyCloak, Cucumber, Selenium.

Jun 2016 - Sep 2016

4 months

Software Developer, Domain Architect

Deutsche Post Direkt GmbH

Relaunch of a Java enterprise application for address rental and new customer acquisition.
Development of a high-performance frontend with an interactive map for area and radius selection.
Implementation of interfaces for document upload/download and automated PDF delivery.
Realization of a runtime scenario with multiple Java processes and Oracle RAC persistence.
Connection of engines for in-memory counting of address data via REST/JSON.
Tech stack: Vaadin, Spring, REST, JSON, JEE, JBoss, Hibernate, Liquibase, Oracle, Maven, Jenkins.

Apr 2016 - May 2016

2 months

Software Development Coach

Haeger Consulting

Teaching Java enterprise skills as part of the internal training project pathfinder.
Building a self-contained Spring Boot application including JPA persistence and a REST interface.
Modeling the application domain and implementing Spring Data repositories.
Training in REST semantics, HATEOAS, and the use of HTTP status codes.
Realization of a responsive frontend with Apache Wicket, Bootstrap, and HTML5.
Introduction to agile methods, issue tracking, and code management with Git/Bitbucket.
Tech stack: Spring Boot, Spring Data, JPA, Hibernate, Wicket, Bootstrap, Git, Maven.

Aug 2015 - Mar 2016

8 months

Software Developer (Fullstack), Technical Coordinator

Bank-Verlag GmbH

Integration of eBanking components with external service providers for authorization of card payments.
Processing of UTF-8 data into TLV structures and ISO8583 messages.
Development of the paydirekt registration application for ad hoc participation during the payment process.
Implementation of a complex workflow with 2-factor authorization and HTTP redirects.
Realization of look & feel tenant capability and feature flags for different banks.
Building a Selenium Grid environment for automated browser tests in the CI build.
Tech stack: Java 8, Spring Boot, Wicket, Bootstrap, Jersey, Hibernate, DB2, Maven, Selenium, Cucumber.

Apr 2015 - Aug 2015

5 months

Software Developer (Fullstack)

Mazda Motors Deutschland GmbH

Development of an iPad-optimized prototype for displaying vehicle stock.
Implementation of progressive disclosure to improve the user experience using JQuery-AJAX.
Use of Apache Wicket as render engine, resource manager, and JSON provider.
Solving CORS issues through preflight requests and HTTP headers.
Implementation of modern UI features such as CSS transitions, infinite scrolling, and slideshows.
Techstack: Wicket, JQuery, Bootstrap, HTML5, Spring Boot, REST, Maven.

Oct 2014 - Mar 2015

6 months

Software Developer (Fullstack)

REWE Systems GmbH

Design and implementation of a big data dashboard for visualizing statistical data.
Development of a web-based information system for managing placement elements in stores.
Implementation of a JPA data layer, a REST interface, and batch processing.
Implementation of security requirements such as SSL encryption and permission concepts.
Provision of SQL migration scripts for DB2 databases.
Techstack: Wicket, Bootstrap, JQuery, Spring, Hibernate, JPA, DB2, JBoss, Maven.

Mar 2014 - Sep 2014

7 months

Software Developer (Fullstack)

Deutsche Post IT Services GmbH

Migration of a call center application to Bootstrap 3 and introduction of new user concepts.
Switch to AJAX communication and REST-compliant resource mappings.
Implementation of server-side validation according to JSR-303 Bean Validation.
Programming of custom controls based on JQuery and introduction of frontend templates.
Optimization of database queries and support with service layer design.
Consulting on search engine integration, schema-less persistence, and the REST paradigm.
Techstack: Bootstrap, JQuery, AJAX, Spring MVC, Hibernate, JPA, Oracle Weblogic.

Oct 2013 - Feb 2014

5 months

Software Developer (Fullstack)

REWE Systems GmbH

Functional extension of the business portal KAM/GFL and refactoring of the persistence layer.
Building a component library based on Wicket, JQuery UI, and Bootstrap for the group.
Development of high-level components such as Google Maps, smart tables, and content sliders.
Support for responsive design to provide a unified codebase for desktop and mobile.
Creation of an application prototype to present Payback data and customer dashboards.
Techstack: Wicket, Bootstrap, JQuery UI, Spring, Hibernate, Solr, DBVisualizer, Subversion.

May 2013 - Sep 2013

5 months

Software Developer (Fullstack)

HRS

Further development and modernization of the eRFP hotel auction platform.
Extension of Vaadin-based frontends and connection to new service components.
Introduction of an event bus to decouple the company framework.
Migration of the frontend platform from Vaadin 6 to Vaadin 7.
Refactoring to improve code quality.
Techstack: Vaadin 7, GWT, Spring, Hibernate, MySQL, MariaDB, Maven, Tomcat.

Oct 2012 - Apr 2013

7 months

Software Developer (Fullstack), Technical Consultant, Concept Author

Mercedes-Benz Trucks

Design of a content information system for delivering internationalized content (Single Source Publishing).
Design of REST interfaces for integration into the corporate infrastructure via SOA.
Design of a content repository based on ISO 639 for managing web and brochure content.
Development of a Web 2.0 administration frontend.
Re-engineering of a web application for profitability calculation (TCO Calculator).
Implementation of financial math algorithms and interactive UI sliders.
Techstack: OSGi (Felix/Karaf), Jackrabbit/JCR, Vaadin, JQuery, Maven.

Jan 2001 - Oct 2012

11 years 10 months

Technical Lead J2EE, Platform Owner, Core Developer

Postbank Systems AG

Many years of development and expansion of the central J2EE multichannel banking platform (TMKP).
Technical lead for the integration of SAP modules such as Account Management and Transaction Banking.
Design of high availability mechanisms (SLA Gold) and connection of backend systems (BS2000, UTM, LDAP).
Modernization of the platform by refactoring around 4000 classes and migrating to new infrastructure.
Development of web frameworks and component kits for online banking and call center clients.
Migration of complex Struts applications to Apache Wicket.
Implementation of a web service gateway for 3D Secure mTan authentication.
Implementation of a K-backup strategy (TXReloader) for recovery after system failures.
Development of J2EE z/OS integrations using the JCA standard.
Setup of test automation tools (Data Driven Testing) and acceptance workflow systems (IVTA).
Techstack: Java EE, Weblogic, SAP, Oracle RAC, Wicket, JAX-WS, JCA, CICS, Maven, Solaris.

Jan 2000 - Present

26 years 7 months

Germany

Initiator, Architect, Developer, DevOps Engineer

Filtech Exhibitions

Relaunch of the domain-driven system landscape with focus on the modules Contacts, Companies, Exhibitors, and Invoicing.
Modularization along clearly defined responsibilities and loose coupling through event-driven communication.
Redesign and implementation of the core modules for partner and exhibitor management based on fine-grained microservices and MongoDB.
Introduction of a diacritic search with Spring and MongoDB for use in an international environment.
Connection of an AI language model to query structured data in natural language (NLP, RAG).
Introduction of e-invoicing according to the ZUGFeRD standard and PDF/A3 format using iText and Mustang.
Execution of extensive system tests against the running stack including REST APIs, security, and messaging.
Upgrade to the latest releases of Spring Boot 3, MongoDB, Vaadin 23, and Kotlin.
Architecture style based on REST/HATEOAS, Domain-Driven Design, and Event-driven Architecture.
Techstack: Java 21, Kotlin, Spring Boot 3, REST, HATEOAS, MongoDB, NATS/JetStream, Spock (BDD Testing), Vaadin 23, iText-Core 9, Project Mustang, Groovy, Docker, NGINX, GitLab CI, Gradle, Maven.

Düsseldorf, Germany

Responsible Developer

CCD • Congress Center Düsseldorf

Development of a location management system for managing building resources and halls.
Implementation of full-text search for room information and floor plan documents.
Implementation of a query mechanism based on event parameters such as room capacity and seating type.
Techstack: Tomcat, Hibernate, Lucene, JDOM, Solaris.

Hamburg, Germany

Responsible Developer, Technical Consultant

Promod Hamburg

Development of a talent and digital asset management system for model agencies.
Management of talent attributes and media assets (set cards, promotion media).
Implementation of a casting function to group talents with hyperlink delivery.
Techstack: Tomcat, Hibernate, Lucene, JDOM, Linux.

Industry Experience

See where this freelancer has spent most of their professional time.

Experienced in Professional Services, Banking and Finance, Retail, Information Technology, Automotive, and Insurance.

Professional Services

Banking and Finance

Retail

Information Technology

Automotive

Insurance

Business Area Experience

See which departments and functions this freelancer has contributed to most.

Experienced in Information Technology, Product Development, Quality Assurance, Business Intelligence, and Customer Service.

Information Technology

Product Development

Quality Assurance

Business Intelligence

Customer Service

Summary

With more than 20 years of professional experience as a software developer and architect, and after various well-known roles working with agencies, corporations, and external partners, Mr. Jarnot handles the many challenges between analysis, design, and implementation of modern information systems. A holistic approach with a focus on the highest quality and reliability, as well as optimization for the target operating platform, is at the center of his work.

Mr. Jarnot relies on the creative combination of established technologies such as Java, Kotlin, Spring Boot, Docker, Spock Framework (BDD), and Apache Kafka with long-proven concepts and architectural styles such as REST/HATEOAS, Domain-Driven Design, Event-driven Architecture, CI/CD, 12-Factor Apps, as well as a focus on security, monitoring, and scalability.

As a senior full-stack developer and technical lead, he has been able to use this knowledge very successfully over many years in the design of interfaces, the integration of legacy backends, the concept and implementation of high-availability systems, the refactoring of monoliths, and numerous rollout projects in a dynamic and heterogeneous application environment.

Many years of experience in agile software development using Scrum and Kanban for the REWE Group, OBI digital, Postbank, HRS, DHL IT Services, Mercedes-Benz, RTL, Bank-Verlag, the AXA Group, and others, as the initiator of a congress and trade fair platform, as a coach for software development with Java, Kotlin, and Spring Boot, and as a contact person for modern architecture and design topics, round off his skill set.

Languages

German

Native

English

Advanced

Statistics

Experience

Total positions 25

Experience in Professional Services 26.5 y

Avg length 2 y

Longest experience 26 y 6 m

Global Experience

Countries worked in 1 (Germany)

Primary country Germany

Expertise

Recent roles Backend Developer, DevOps Engineer, Solution Architect, Developer, Software Developer, Coach

Main industries Professional Services, Banking and Finance, Retail

Main business areas Information Technology, Product Development, Quality Assurance

Profile

Created

June 2025

Last Update

July 2026

Need a freelancer? Find your match in seconds.

Try FRATCH GPT

Frequently asked questions

Have questions? Find more information here.

Thomas is based in Bonn, Germany and can operate in on-site, hybrid, and remote work models.

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

Thomas has at least 27 years of experience. During this time, Thomas has worked in at least 18 different roles and for 21 different companies. The average length of individual experience is 1 year and 2 months. Note that Thomas may not have shared all experience and actually has more experience.

Based on recent experience, Thomas would be well-suited for roles such as: Backend Developer, DevOps Engineer, Solution Architect, Developer, Software Developer, Coach.

Thomas's most recent position is Backend Developer, DevOps Engineer at AXA Digital Experience.

In recent years, Thomas has worked for AXA Digital Experience, REWE digital, Mesalvo, ALD Automotive, and REWE Systems.

Thomas is most experienced in industries like Professional Services, Banking and Finance, and Retail. Thomas also has some experience in Information Technology, Automotive, and Insurance.

Thomas is most experienced in business areas like Information Technology, Product Development, and Quality Assurance. Thomas also has some experience in Customer Service and Business Intelligence.

Thomas has recently worked in industries like Professional Services, Retail, and Information Technology.

Thomas has recently worked in business areas like Information Technology, Product Development, and Quality Assurance.

Thomas will be available full-time from January 2027.

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

To hire Thomas, click the Meet button on the profile to request a meeting and discuss your project needs.