IntelliJ IDEA Expert in Hamburg

• Designed and implemented a Python-based ETL pipeline with the Dagster framework to transform raw energy data from heterogeneous sources using InfluxDB and visualizations in Grafana
• Defined time-based and dependency-based jobs
• Deployed to managed Kubernetes clusters using Helm
• Integrated InfluxDB Cloud
• Prepared data for use in Grafana, including cleaning, normalization, and time-based resampling in Python
• Developed dashboards and visualizations in Grafana
• Developed unit tests with mocking using pytest
• Set up a CI/CD pipeline in GitLab

Technologies: Python, Dagster, InfluxDB, Grafana, pandas, pytest, REST, CI/CD, GitLab, Container, Kubernetes, Helm, Docker, Cloud

• Reviewing functional and technical requirements from a testing perspective
• Creating test cases and automated tests to validate requirements
• Performing manual and automated functional, end-to-end, and regression tests
• Documenting test results and tracking defects
• Using models like GPT-4, BERT, and Hugging Face Transformers for automated test case generation, analysis of test results, and improving test coverage, including bias checks and security reviews
• Techs: MS Office, Jira, Zephyr, Confluence, Tosca, stakeholder communication, Agile, Kanban, Scrum, OpenAI API, Hugging Face, PyTorch, LangChain.

• Development of modern web applications focusing on React and Next.js

• Implementation of e-commerce and business platforms for SMEs

• Analysis and optimization of software and data structures

• Design and development of custom IT solutions

• Structuring of data flows and system architectures

• Ongoing project work in web development and platform solutions

• Tax Advisor Platform with Client Portal and Admin System:

• Development of a web-based platform with an integrated client portal

• Implementation of a system solution including a website, admin panel, and client application

• Development of a role-based access system (admin / client)

• Implementation of document and invoice management

• Digitization of business processes

• Building high-performance frontend structures

• Integration of APIs and backend logic

• Coffee Business Platform with Admin System:

• Development of a web application for a café with administrative functions

• Implementation of internal workflows and user management

• Structuring of digital business processes

• Development of modern UI components with a focus on performance

• Shared Account Platform (Admin & Client Applications):

• Development of a scalable platform with separate applications for admins and users

• Implementation of a role-based access system

• Development of a modular frontend architecture with React and TypeScript

• Integration of API structures and data management

• Integration of SAP Commerce Cloud with SAP Cloud for Customer
• Creation and execution of unit and integration tests
• Error analysis and bug fixing

• Designed, implemented, and deployed two new microservice components, enabling new business functionalities and supporting regulatory compliance for enterprise clients.
• Ensured business continuity and system reliability within a high-transaction, microservice-based environment, taking ownership of backend systems under dynamic business conditions.
• Identified and refactored inefficient implementations, applying cost-benefit analysis to optimize performance, maintainability, and code quality.

• Working with developers, security, and operations teams to align requirements
• Supporting product owners and development teams in using logging and monitoring solutions based on the Elastic Stack
• Developing and standardizing log schemas as well as defining practical standards for observability
• Designing and further developing logging architectures for complex, distributed multi-tenant environments
• Connecting application and infrastructure logs as well as security tools and metrics
• Optimizing data flows and modeling for analysis and reporting purposes
• Building automated infrastructures using Terraform/Terragrunt and Ansible
• Maintaining and further developing CI/CD pipelines in GitLab as well as automated development environments in Hetzner Robot
• Operating and automating Proxmox clusters including Ceph storage
• Setting up and operating Kubernetes (k3s) clusters on Fedora CoreOS including base services such as Vault, OpenLDAP, and HA Proxy
• Implementing security-critical infrastructures according to BSI baseline protection and securing existing systems
• Supporting the operation of solutions in cloud environments (including AWS)
• Working in agile teams using Scrum and Kanban
• Technologies/ applications: Elastic Stack (Elasticsearch, Logstash, Beats/Elastic Agent, Kibana), Terraform, Terragrunt, Ansible, GitLab CI/CD, GitOps, Proxmox, Proxmox Ceph, Kubernetes (k3s), OpenShift, Helm, Kustomize, Vault, OpenLDAP, HA Proxy, Hetzner Robot systems, AWS, Prometheus, Grafana, Syslog Linux/Windows, Docker, NGINX, Apache Security & Compliance (BSI baseline protection, SIEM/SOC)

• Migration of a case processing system with numerous interfaces to other systems from Spring and Activiti to a Java JEE application
• Further development into a cloud application
• Consulting, development, requirements analysis, specification and design
• Coordination with upstream and downstream systems
• Data modeling, programming and implementation
• Support with code reviews and ensuring clean code in the PL/SQL context
• Documentation in Confluence
• Troubleshooting PL/SQL applications including log analysis, session tracing and performance profiling
• Optimization and tuning measures in the PL/SQL environment
• Knowledge transfer and onboarding of new employees
• Use of Jira for task management, progress tracking and sprint planning

• Further development of a finance layer for subscription and one-time purchase billing and accounting.
• Technologies: Kotlin, AWS (SQS, S3, ElastiCache, Aurora), React, TypeScript, Coroutines, IntelliJ IDEA, Spring (Boot, Data, WebFlux), JUnit, Testcontainers, Cucumber, Liquibase, PostgreSQL, Webservices (REST), R2DBC, OpenAPI 3, Gradle, GIT, Docker, Netty, GitHub Actions, Jira/Confluence, arc42

• Coaching junior developers
• Further development and customer-specific extensions of a standard software product (microservices (DDD) and partly monolith)
• Interface extensions
• Web services
• Test automation
• Design
• Technologies used: Java8, Java17, TypeScript, Python, PostgreSQL, Spring (Integration, Data, Boot), JPA, AWS (Cloud, Lambda, EC2, SQS/SNS), Microservices, Fitnesse/Cucumber, Gitlab

• Further development of the compliance products
• Role responsibility as a Senior Software Engineer
• Team size: 5 - 15 people
• Tools: TypeScript, Angular 18, Node.js, Nest.js, AWS, Kubernetes/Helm Charts/Docker, GitLab (CD/CI), Elasticsearch, MySQL, OpenAI, Java, RabbitMQ

• Analyze business processes to evaluate test automation
• Develop and execute automated tests (Web & Mobile)
• Perform manual tests to cover non-automated areas
• Handle bug fixing, reporting, and documentation of all test results
• Coordinate with teams and product owners for test optimization and requirement analysis
• Conduct component tests, system tests, and migration tests
• Create monitoring reports and error analyses according to process guidelines
• Participate in the team for Deutsche Bahn’s new DB Navigator app during the software reorientation; responsible for new workflows, modern design, and replacing the old systems
• Tools: Appium, Selenium, Cucumber, Android Studio, IntelliJ, GitLab, Instana, Java, iOS, CSS

• Reimplementation of the ESN.com online shop with Shopify's Hydrogen and Remix
• Headless CMS Contentful integration via GraphQL

• Contributed to the development of the Rubix editorial system
• Implemented various microservices based on Java, AWS S3, AWS SQS, AWS SNS, and Spring Boot, deployed to AWS ECS and AWS Fargate
• Designed and developed AWS Lambdas using TypeScript
• Used PostgreSQL in an AWS RDS Aurora cluster and AWS DynamoDB
• Implemented continuous deployment with GitLab pipelines
• Built an Infrastructure as Code environment with AWS CDK
• Set up and maintained a monitoring platform using AWS CloudWatch
• Developed various frontend components with Vue.js
• Designed the microservice architecture applying Domain Driven Design and GraphQL interfaces

• Operation and further development of the inventory system for booksellers (Quimus). It is an in-house development by Libri that is sold to customers as Software as a Service. The software is developed in an agile way by two developer teams (about 5 developers each). The software consists of around 25 Java microservices that mainly communicate via messaging and share a common Angular frontend. The application runs on Kubernetes in AWS.
• Technologies used: Java 17 & 21, Spring Boot 2 & 3, Hibernate, MySQL, Spring Cloud AWS, Lombok, AWS SQS, AWS SNS, AWS RDS, AWS S3, DynamoDB, Kubernetes, Docker, OpenSearch, Hibernate Search, Liquibase, Gradle, Terraform, Helm, GitLab CI, Keycloak OAuth2, TypeScript, Angular
• My focus until December 2023: Connecting additional POS systems to the inventory system. Connecting the data warehouse for report display. Extending existing features (goods receipts, invoicing, item management, ...). Operations and DevOps tasks.
• Focus from January 2024: Extracting the product search from the inventory system into a global service to use in other applications. Integrating the product search into the booksellers' online shops (also run by Libri). Importing and providing digital items in the product search.