Marc S.-Fullstack Engineer | Java & Spring Boot | Angular | System Integration

PLANT-MY-TREE®-per-order

The application enables Shopify merchants to automatically place tree-planting orders for every incoming order. By integrating ecological contributions directly into the purchase process, the manual effort for tracking and billing reforestation initiatives is eliminated. The system increases transparency for end customers through real-time visualizations of the ecological impact directly in the storefront. The architecture is based on a modular monolith with Spring Boot in the backend and an integrated React app inside the Shopify admin area. The solution uses webhooks to capture order data in an event-driven way and integrates the weclapp ERP system for automated monthly invoicing. An app proxy mechanism provides dynamic statistics such as CO2 compensation and planted trees without any performance loss for the merchant shop.

Tasks:

• Design of the modular software architecture based on Spring Modulith to ensure high maintainability
• Development of the event-driven business logic for evaluating Shopify orders via webhooks
• Implementation of automated invoicing by connecting the weclapp REST API
• Building the frontend using React Router and Shopify App Bridge for native integration
• Design of the database model and implementation of the persistence layer with JPA/Hibernate and Prisma
• Integration of internationalization processes for global use in the frontend and email communication
• Automation of deployment processes using Docker and GitLab CI/CD

Project skills: Java 25, Spring Boot, Spring Security, Spring Modulith, Hibernate, JPA, REST API, PostgreSQL, Maven, Liquibase, React, TypeScript, React Router, Vite, Node.js, Prisma, Zod, Docker, Docker Compose, GitLab CI/CD, Shopify CLI, Shopify App Bridge, Polaris, weclapp, i18next, Lombok, Vitest

Certificate Personalization

Certificate Personalization is an automated web application for personalizing and distributing certificates for trees or corals. The system digitizes the process from retrieving order data from the ERP system (weclapp), through the dynamic generation of PDF certificates, to the automated sending to end customers. Manually creating personalized certificates for high order volumes creates significant administrative effort. Certificate Personalization solves this challenge through seamless integration into the existing system landscape and a highly automated processing pipeline.

Tasks:

• Design and implementation of the entire system architecture with a focus on scalability and maintainability
• Development of robust API clients and webhook handlers for automated synchronization of orders and customer data
• Implementation of a flexible PDF generator for creating personalized certificates with dynamic content (locations, coordinates)
• Building an email delivery service with integrated logging and retry logic for reliable certificate delivery
• Design and implementation of an intuitive dashboard for managing orders and manually reworking certificate data
• Implementation of JWT-based authentication and role-based access control (Spring Security) as well as ensuring data consistency

Project skills: Java 25, TypeScript, SQL, HTML5, CSS3, Spring Boot, Spring Security, Spring Data JPA, Angular 22, RxJS, Hibernate, weclapp, Webhooks, OpenAPI / Swagger, Docker, PostgreSQL, Liquibase, GitLab CI/CD, Maven, Git, JUnit, OpenAPI Generator, JWT, DevOps

Project-Scout

Project Scout is an AI-supported acquisition system for automating the sales process for IT freelancers. The application aggregates project postings from various sources, performs AI-based semantic matching against individual skill profiles, and generates context-sensitive application letters as well as real-time alerts.

Tasks:

• Design and implementation of a reactive microservice architecture based on Kotlin (Quarkus) and TypeScript (SvelteKit)
• Development of a semantic scoring system using LangChain4j to match project requirements with individual skill profiles
• Implementation of robust API clients and scraping mechanisms for continuous data extraction from external project portals
• Building an AI assistant with tool support (function calling) that performs complex database queries and generates statistical analyses
• Integration of a real-time notification logic via the Telegram API to immediately inform about highly relevant 'high-match' opportunities
• Development and optimization of specialized system prompts for generating individual, context-based application letters without marketing buzzwords

Project skills: Kotlin 2.4.10, Java 25, TypeScript, SQL, Quarkus, SvelteKit, Hibernate, TailwindCSS, LangChain4j, LLM Integration, Prompt Engineering, Agentic AI, Docker, PostgreSQL, REST-APIs, WebSockets, Telegram API, Git, Maven, DevOps

NEWPOSS Backoffice

NEWPOSS Backoffice is a Java EE-based enterprise application built on the TREND framework. The software supports store management and store staff with cash management, reporting, user administration, and the import and export of master and transaction data. As part of the modernization, individual modules were gradually migrated from the monolith to Spring Boot.

Tasks:

• Developed and maintained a Java EE-based enterprise application built on the TREND framework
• Designed and implemented new backend features and business requirements
• Worked on the gradual migration of individual modules from Java EE to Spring Boot
• Created and optimized REST and SOAP interfaces
• Conducted code reviews and ensured development standards
• Developed support and analysis tools for 3rd-level support
• Created and optimized reports
• Analyzed and fixed complex software issues in the productive enterprise system
• Developed automated tests with JUnit and ensured quality with SonarQube
• Worked in an agile Scrum team

Project skills: Java 8/21, Java EE, TREND Framework, Spring (Boot), Microservices, Thymeleaf, Git, GitLab, Jenkins, WildFly, Tomcat, JUnit, PostgreSQL, Jira, Confluence, ServiceNow, Liquibase, REST, SOAP, Powershell, Docker, OpenAPI, Scrum, SoapUI, OSGi, Maven, Nexus, SonarQube

WSCorner

Interactive online platform for virtual football clubs with a focus on match simulation, transfer market, youth development, and community competitions.

Tasks:

• Migrated legacy PHP components to modern Spring Boot services
• Developed and optimized complex simulation logic for match and tactic calculations
• Continued development of the youth and market value system
• Optimized database queries and backend processes for performance
• Set up monitoring with Prometheus and Grafana to analyze API performance and system metrics
• Containerized the development environment with Docker
• Developed and maintained REST and GraphQL interfaces

Project skills: Java 21, Spring Boot, Spring Data JPA, Hibernate, MySQL, Liquibase, Vue.js, GraphQL, REST, Docker, Prometheus, Grafana, Maven, Git

Books App

The Books App makes it easy to organize books and authors. Users can create author profiles, add books, attach images to them, and assign them to the right authors. The app offers an intuitive user interface and is ideal for managing personal book collections.

Tasks:

• Development of the backend system with Java EE
• Development of the frontend system with Angular
• Deployment of the software on a Linux server
• Customer communication
• Migration from Java EE to Spring Boot

Project skills: Java 25, Java EE, Angular 22, RxJS, Spring (Boot), Linux, Tomcat, MySQL, WordPress, SVN, JavaScript/TypeScript, HTML5, Liquibase, REST, Docker, Test-Driven Development, Maven, PWA