Analyzed a 20-year-old, large-scale Java/Tomcat application (~2M

LOC) to propose a comprehensive modernization strategy using

AI-assisted tooling.

- AI Migration PoC: Developed a proof-of-concept leveraging AI

models to automate the migration of legacy JSP pages to modern

React components.

- Architecture Audit: Evaluated a custom Servlet-based backend

(no Spring/JEE) with ~0% test coverage; streamlined ongoing

migrations (Firebird to PostgreSQL) and redundant React state

management in a mixed JS/TS codebase.

- Production & Cluster Support: Resolved critical live-system issues

in a clustered environment, focusing on session handling,

Server-Sent Events (SSE), and license counting.

- Tech Stack: Java 11, Tomcat 9, Redis, PostgreSQL, Firebird, React

(JavaScript/TypeScript), Docker Compose, Claude, Codex, Gemini

CLI, IntelliJ.

Focused on upskilling and hands-on deep dives into

emerging technologies to expand my freelance service

portfolio. Developed several proof-of-concepts (PoCs)

and independent projects, including:

- CMDBlite: A lightweight, multi-tenant CMDB system with

integrated monitoring capabilities.

Tech Stack: Java, Quarkus (native build), SQLite, plain JavaScript,

htmx, Qute templating, Server-Sent Events (SSE), Docker.

- HN Client for Hacker News (Published Android App): A

minimalist Hacker News reader featuring a custom archive

function.

Tech Stack: Kotlin, Ktor-Client, Room (SQLite), Google Firebase,

on backend: Quarkus, REST, SQLite.

- AI Integration & Tooling: Evaluated capabilities and integration

patterns of the Gemini CLI AI tool.

• Worked on a fiscal and security risk analysis of the customs administration and the investigation services project
• Maintained and extended a JEE/Spring based risk management system with a JSF/PrimeFaces frontend and Oracle database
• Except for the daily business as bugfixing and different requirement implementations this are the most interesting parts on which i worked on:
  • worked on a new powerful, Elasticsearch based, search architecture as a replacement for a legacy Oracle DB based solution
  • migrated EJB-Services to Spring
  • migrated RIKO-Application from JBoss-EAP 7.4 to 8.0 together with Spring Boot from 2.7 to 3.3 including Hibernate and major CI/Jenkins adjustments
  • migrated (code rewritten) from deprecated Elasticsearch REST Client Library to the current Elasticsearch Java Client Library
  • optimized huge MS-Excel file import process by switching to streaming technology
• Supported requirement engineers
• Supported developer and test colleagues
• Prepared Oracle DDL scripts

• Worked on an ERP system project
• Implemented requirements and bugfixes on an existing ERP system
• The ERP system based on a proprietary Java framework (TREND-Framework), which was used to extend and create GUIs, implement the business logic and test it

• Worked on a checkout/till and related backoffice system
• Implemented requirements and bugfixes on an existing codebase based on a proprietary Java framework (TREND-Framework) and tools
• Main topics were: analyse requirements and bugs, extend and design till process workflows, extend and design reports, extend and design REST and SOAP interfaces for data import/ export, code refactoring, define and write integration and unit tests, documentation, release preparation
• Worked on a Python script for documentation export from proprietary documentation system (TREND-Analyst) to Atlassian-Confluence
• Supported developer and test colleagues
• Participated in code reviews

• Worked on the DAC 6 project (DAC 6: EU tax disclosure rules)
• Designed and implemented an Application based on Spring Batch Jobs to process tax arrangement data
• Main topics were: technical sub-system design and documentation, generate large XML files (up to 100 MB) with JAXB, implement Oracle PL/SQL Procedures, Reporting SQL Views, different types of tests (Unit-Test; Integration-Tests; System-Tests; Stress-Tests)
• Developed a WebApplication GUI with JSF/PrimeFaces with strict accessibility requirements especially for blind users
• Defined JUnit and Selenium Web-GUI tests
• Prepared Jenkins jobs
• Supported developer colleagues
• Supported test team
• Participated in code reviews

• Implemented a GUI for a telecommunication carrier incident management system with PHP Symfony-Webframework and Vue.js
• Supported the backend team on Spring Boot microservices development
• Designed an external order interface architecture
• Implemented a GUI for a product configuration system with PHP Symfony-Webframework and JavaScript

• Implemented CoreWallet payment gateway integrations for client-specific, local PSPs including corresponding payment method setup and routing
• Implemented a Processing and Routing Engine for Payments
• Implemented client-specific SPAs with Ember.js
• Implemented an SBE test framework and an exhaustive suite of SBE tests for a large client project
• Software engineer on the CoreWallet, balancr and CoreExchange products
• Implemented a highly customizable Sport Event Android App
• Integrated Google Maps and HERE Maps in Android
• Introduced GPS-Tracking and Video Playback
• Integrated AWS Push-Notifications/ Amazon Simple Notification Service (SNS)

• Developed on a Deployment/Release Management System

• Developed a Billing System which unified billing data from multiple legacy systems
• Developed a CRM System
• Developed several services and tools for Telecommunication typical scenarios (VPN-, Telephony-/ Fax-, Telecommunication Port - Management Systems)
• Implement Oracle PL/SQL Procedures for data synchronisation

• Developed Java Applet, Struts and MS Excel VBA Applications for a natural gas exchange platform
• Developed a SOA sub system for message interchange with third-parties

• Developed a highly customizable Billing System for TV-Commercials in context of AdManagement/ Sales System
• Developed several Data Import/Export interfaces and tools
• Developed several Data Migration PL/SQL Scripts
• Developed several Report Data Collectors

• Implemented a Industry Roboter Controlling Application on Windows Embedded CE device

• Implemented a Sync Web Tool to German Insurance Association (GDV)