GitHub Experts

Maturing their API practices on both a business and technology level. My role covers strategy, architecture, developer advocacy as well as hands-on software engineering, enabling both technical teams and business leadership to adopt and act on API-centric principles effectively. Coincidentally, we also establish GitOps, DX and platform best practices with this project.

Highlights:

• Aligning executives with the initiative by clarifying strategy, replacing misconceptions and myths with facts, clarifying the value of existing assets and enabling informed decision-making
• Formulating a way forward for API Lifecycle Management at OTTO
• Driving platform progress and fostering developer engagement by hands-on engineering work towards strategic goals

API Lifecycle Management, Team Topologies, Organizational Evolution, Regulatory, Platform Advocate, Developer Platform, Communities of Practice, Terraform, Kotlin, Kafka, Kong, WSO2, Apigee, Gravitee, Backstage, AsyncAPI, OpenAPI, API Design, AWS, React, Node.js, TypeScript, Redocly, reactive programming, CDC, Golang, Gin, GitOps, DX (developer experience), stakeholder management, roadmaps, workshops, discovery.

• Developed a browser-based platform for Kubernetes no-code deployment and cluster management
• Developed a CLI in TypeScript to deploy resources in the cluster without leaving the browser UI.
• Implemented DevSecOps pipelines: image scanning, SBOM, policy enforcement, supply-chain security, and used Kyverno. Implemented IAM integration for the command-line utility tool.
• Designed role and permission models for Keycloak, OAuth/OIDC, and social login flows.
• Used LLMs to convert user intent into diagrams.
• Worked on integration with multiple sovereign clouds like StackIT, Hetzner, CIVO, UpCloud, plus public clouds like AWS, GCP, and Azure
• The technology stack includes Java, Spring Boot, Kubernetes, OpenAI, Kubernetes multi-tenancy using vCluster, Karpenter, RBAC for CLI, Helm, React

Reporting and controlling with Power BI for a productive ERP system

• Analysis of ERP data and interfaces for use in Power BI dashboards
• Evaluation and migration of existing reports (e.g. Excel) to Power BI
• Development of an access rights concept for selective data access
• Documentation and training on how to use and adapt the Power BI dashboards

Label: Power BI, Excel, SelectLine ERP, Microsoft SQL, SQL Server Management Studio

Built an international e-commerce platform for a multi-vendor marketplace for digital assets from scratch. Designed and operated cloud native architectures at enterprise scale.

• Designed and operated a highly scalable microservice and serverless architecture
• Built the complete cloud infrastructure with Terraform + AWS CDK in AWS
• Provisioned ECS/EKS clusters (Fargate), Application Load Balancers (reverse proxy), and Lambda functions
• Observability & tracing with CloudWatch, DataDog, Prometheus, and Grafana
• End-to-end setup with DataDog (formerly AWS CloudWatch), Prometheus, and custom Grafana dashboards
• Integration of advanced metrics (including ORM mapper) and distributed tracing with Jaeger
• Robust backup and disaster recovery strategies
• RDS Postgres backups and hourly snapshots
• Read-only, asynchronously synchronized replicas with automated master failover in emergencies
• Minute-level rollback capability through versioned Docker images on ECS and Git-based CI/CD pipelines
• Created CI/CD pipelines with GitHub Actions for automated multi-stage deployments (Dev, Testing, Prod)
• Integrated Stripe for international payment processing
• Built a marketplace payment system with multiple parties and payout routines
• Used Algolia for high-performance real-time search of digital assets on the platform
• Federation of services with GraphQL and Hasura
• Later migration to GraphQL Mesh
• Test Driven Development (TDD) - unit, integration, and E2E testing with Jest, Vitest, and Playwright
• Used Next.js / React for modern frontend applications in the nx monorepo
• Enterprise security architecture & access control
• Integration of JWT tokens with Auth0, OAuth, OIDC, IP guards, BOLA protection, and secret vaults
• Authorization concepts with RBAC, ABAC, and native Postgres Row-Level Security (RLS)
• Built internal microfrontends with Retool for fast prototyping and operational business processes

Technologies: ABAC, AWS CDK, AWS CloudWatch, AWS ECS, AWS EKS, AWS Fargate, AWS RDS, AWS S3, Algolia, Auth0, DataDog, Docker, GitHub Actions, Grafana, GraphQL, GraphQL Mesh, Hasura, JWT, Jaeger, Java, JavaScript, Jest, Kotlin, Kubernetes, Monorepo, Next.js, OIDC, Playwright, Postgres, Postgres RLS, Prometheus, RBAC, Redis, Retool, Serverless, Stripe, Terraform, TypeScript, Vitest

• Worked as freelance Senior DevOps Consultant on-site for IBM at a European Union Agency, operating in a highly secure, air-gapped environment managing classified systems.
• Led automation and DevOps initiatives for a large-scale OpenShift platform (>400 nodes), driving deployment efficiency, GitOps adoption, and operational automation using Ansible, Python, and Bash while ensuring compliance with security requirements.
• Spearheaded automation of release and deployment workflows in a private cloud environment hosting 400+ OpenShift nodes, significantly improving deployment speed and reliability.
• Migrated existing playbooks, roles, and templates from Ansible Tower to Ansible Automation Platform (AAP), ensuring full compliance with fully-qualified collection names (FQCN) and preparing custom Execution Environments (EE) for containerized automation.
• Implemented GitOps Agent for AAP Controller Configuration as Code, enabling automated synchronization (CRUD) of Ansible Controller objects based on repository-stored configuration definitions using GitHub webhooks.
• Designed and automated complex multi-step operational workflows including environment cleanup, Helix cluster component re-creation, Kafka topic management, and OpenShift object lifecycle management across ~100 environments.
• Achieved a reduction of multi-day manual operations to under a few hours through automation improvements spanning multiple AAP clusters and OpenShift environments.
• Integrated Ansible Automation Platform with Thycotic (Delinea) Secret Server via lookup plugin to enhance secure credential management in automated processes.
• Managed deployment tasks, platform troubleshooting, and Istio network configurations while adhering to stringent EU PSC security and compliance standards.
• Collaborated with infrastructure and application teams to refine deployment procedures, develop naming conventions, and continuously improve automation coverage in an air-gapped, classified environment.

I support the development of an industrial automation and communication product in which hardware, firmware, embedded software, system architecture, and testing work closely together. As a coach and technical sparring partner, I support product and project owners as well as development teams in turning product goals into a clear technical delivery structure.

• Technical Vision & Strategy: translated product goals into prioritized requirements, milestones, decisions, and executable work packages for HW-/SW teams.
• HW-/SW Collaboration: structured the interfaces between hardware, firmware, Embedded Linux/RTOS, fieldbus/connectivity, system test, and product management; made risks and dependencies transparent.
• Coaching & Leadership Sparring: clarified roles, responsibilities, prioritization, and decision paths with technical leads and teams and strengthened cross-disciplinary collaboration.

Methods & environment: Polarion, GitHub, requirements engineering, configuration management, PROFINET, embedded systems, agile delivery, coaching, and facilitation.

• Development of an AI-powered project organization tool for a civil engineering company that intelligently links project, task, tender, schedule, and document data through a knowledge graph.
• Implementation of AI features for document analysis, information extraction, context-based assistance, and voice-based data capture based on Microsoft Azure AI, reducing administrative effort, making information available faster, and supporting project teams in decision-making.
• Tech stack: Python, React, TypeScript, FastAPI, Claude Code, Codex, Graphify, PostgreSQL, Microsoft Azure AI Foundry, Azure OpenAI, Azure AI Speech, Azure AI Document Intelligence, Microsoft Graph, Microsoft Entra ID, Docker, Git, CI/CD.

Product:

• Built a production-ready AI platform for generating brand-aware marketing images and videos from product data, user requirements, and uploaded media.
• Own the platform architecture, technical roadmap, API design, security, deployment workflow, operational reliability, and model-provider strategy.
• Developed the core platform in .NET and built supporting AI and workflow prototypes in Python, applying language-independent API contracts and structured interfaces between services and model providers.
• Implemented reliable background processing with RabbitMQ, persisted workflow state, idempotent handling, retries, failure recovery, logging, secure storage, authorization, and credit accounting.
• Made pragmatic build-versus-buy and model-routing decisions based on reliability, latency, cost, and maintainability rather than novelty.

Agent Orchestration & RAG Systems

• Built and compared agent workflows using Microsoft Agent Framework, LangGraph, and LangChain, including tool use, conditional routing, clarification steps, state management, and hand-offs between agents.
• Implemented reusable .NET components for agents, prompts, tools, model providers, structured responses, and retrieval with pyvector, making it easier to change AI providers without rewriting the core workflow.

Sub-project lead in an agile IT environment

Leading a software development team (10 employees)

• Leading a software development team with 10 employees
• Budget responsibility approx. 3 million euros per year
• Conducting employee and job interviews
• Responsibility for resource planning (budget and employees)
• Digitalization of a web interface
• Regular reporting to customers and stakeholders (C-level)
• Product management: developing and implementing product strategies; defining requirements to guide product development
• Structuring product development & continuous testing efficiently to quickly incorporate feedback & compliance points
• Close collaboration with stakeholders & various teams to understand requirements, set priorities, ensure rollout, and increase user-friendliness
• Project experience in an energy industry company, including the functioning of energy markets, the basics of energy generation and distribution, as well as current challenges and developments in the industry
• Project experience in the railway sector - including the structure and operation of railway systems.
• Project experience within the 16.7 Hz traction power sector incl. knowledge of regulatory processes
• Formulating the sub-project charter and the project profile according to the project standard together with the project management
• Controlling service delivery according to the project charter
• Planning and controlling human resources including budget planning for the sub-project
• Ensuring the work capacity of the sub-project participants, e.g. by requesting access rights and documents for the sub-project team
• Planning and control for the respective sub-project (time, scope, budget) including the creation of necessary documents
• Alignment with the business department and Product Owners to plan the sub-project scope and the corresponding implications
• Executing milestone planning according to the agreed process model
• Effort estimation and support of sub-project controlling as well as overall project controlling in forecasting and planning
• Reporting sub-project status (according to status slide template) including progress (according to progress measurement)
• Analyzing, preparing, and addressing action and decision requirements
• Escalating sub-project issues to the project management
• Creating and managing Change Requests (CR)
• Quality assessment of completed task packages from a project management perspective (time, scope, and budget)
• Implementation management of the overarching guidelines and requirements in the sub-project, supported by cross-functional roles on the functional and technical side.
• Identifying, managing, documenting, and communicating opportunities, risks, and dependencies within and across sub-projects
• Supporting project management in creating the overall project plan and overall status reports
• Preparing and managing commissioning including the required documents and protection needs assessment

Scrum Master in an agile IT environment supporting a software development team in the full-stack area (7 people)

• Close collaboration with stakeholders & various teams to understand requirements, set priorities, ensure rollout, and increase user-friendliness
• Implementation of the selected Scrum method, including the required events, meetings, artifacts (product backlog, sprint backlog, burndown charts), metrics, as well as conducting required training in an agile IT environment
• Preparation of Scrum events such as Daily, retrospectives, Review, Sprint planning, estimation, and refinement (agile way of working)
• Moderation of retrospectives and elimination of obstacles to move the team and product forward
• Preparation of action items and retros via whiteboard and Figma
• Application and improvement of agile methods such as Kanban, Scrum, SAFe, or Scrum of Scrums
• Tracking the "Definition of Done" and "Definition of Ready" for all work results of the development team
• Advising on information flow and communication improvements between Product Owner and project team
• Experience with automation, validation such as mandatory field checks, notification functions, creation of filters, boards, and reports via JQL, and setting up cycle time
• Use of Jira & Confluence
• Setting up a progress measurement for project management to transparently map planned vs. actual team capacities and actual efforts for user stories
• Measuring team progress: creating team KPIs: "velocity", "burn-down chart", "throughput", "costs", "quality", "scope"
• Evaluation of agile metrics, process management, and process modeling methods (BPMN, EPC, UML)
• Communication and moderation know-how
• Methodological competence proven in conflict discussions

• Recurring problem in my own AI-supported projects: requirements analysis, use cases, and architecture decisions can be created quickly with AI support, but they remain hard to trace and are scattered across markdown files – knowledge is lost as soon as it is no longer in the context window. arknet turns requirements engineering and architecture knowledge into structured, testable data instead of plain text: requirements, use cases, and architecture decisions as a consistently linked knowledge graph, traceable from the requirement to the architecture decision – queryable for humans and AI agents alike. Built technically on RDF/OWL and its own MCP server.

• Result: MCP daemon running, Docker image automatically published on GHCR, nine hexagonal modules, eleven ADRs (including an open-core license model). Requirements engineering and ubiquitous language hexagon active. Publicly available as a Community Edition under Apache-2.0 since 07/2026 (github.com/kogn-io/arknet), together with the Claude Code plugin and the GHCR image; open-core model.

• Label: Java, Maven, RDF, RDF4J, OWL, SPARQL, Model Context Protocol, Spring AI, Docker, GitHub, Git, Claude Code, Obsidian, DDD, Hexagonal Architecture, ArchUnit, JUnit, AssertJ, interface development, Software Architecture, Continuous Integration, Knowledge Management

• Modernization of a large-scale Java enterprise application*

The project is modernizing a complex enterprise application that has grown over many years. The existing Spring-based legacy system runs on Java 8, OSGi, and Eclipse RCP and is being gradually migrated to a modern, maintainable architecture with Java 25 and Quarkus.

Marcus works on analysis, architecture, refactoring, and implementation. One focus is on untangling historically grown structures and dependencies and on building a clean, sustainable Java and Quarkus technology stack.

Tools & technologies: Java 8, Java 25, Quarkus, Hibernate ORM with Panache, EclipseLink, OSGi, Eclipse RCP, Maven, JUnit, Mockito, REST, JSON, Git, Eclipse IDE, IntelliJ IDEA Ultimate, Jira, Confluence

• Analysis of the existing CAN communication between microcontrollers
• Analysis of the sensors used and the measured values collected
• Planning the CAN messages for transmitting the measured values
• Iterative adjustment of the microcontroller code to the new CAN messages
• Cross-compilation from x64 to arm64

Workflow-automation SaaS for operations teams (Berlin, 120 people); full-time freelance engagement reporting to the CEO: an initial 12-month interim mandate, extended twice through the AI build-out; owned product for one squad and coached the other product managers on process.

• Led generative AI (LLM) integration into the core product: from LLM-powered steps to natural-language workflow authoring and step-level automation suggestions, plus AI-managed dynamic workflows, shipped behind eval gates with human-in-the-loop fallbacks: AI-drafted workflows grew to 31% of all new workflows, and median time-to-first-workflow fell from 3 days to 4 hours.
• Packaged the AI capabilities as a usage-based add-on priced on executed automation steps, working with sales and marketing on positioning: ~€800K added ARR in the first year, and adopting accounts churned 1.8 pp less.
• Owned the roadmap end to end: replaced feature-request-driven quarterly planning with an outcome-based rolling roadmap built on quarterly bets and explicit kill criteria, presented monthly to the executive team and quarterly to the board.
• Rebuilt the product-management operating system: weekly customer-discovery cadence incl. workshop facilitation, RFC/decision-doc reviews and a single quarterly metrics narrative; coached four product managers, one promoted to senior during the engagement.
• Closed the engagement as scoped: hired and onboarded the permanent VP Product, handed over the process playbook and roadmap, and exited on schedule in June 2026.

• Further development of the existing e-commerce platform based on SAP Commerce (Hybris) to meet the growing demands of digital commerce.
• Ensuring the scalability and performance of the backend, so the platform remained stable and efficient even under heavy user load.
• Development and integration of new OCC REST APIs and services for modular extensions and flexible adjustments, to implement new features quickly.
• Optimization of data flows and interfaces, which significantly improved platform efficiency and system performance.
• Ensuring a maintainable and scalable code base by using Clean Code principles, proven design patterns, and a future-proof architecture.
• Reduction of errors through extensive testing with JUnit, Mockito, and load tests with Gatling, supported by the introduction of automated test processes.
• Improved system performance through targeted refactoring measures and efficient database queries, especially to handle peak loads.
• Use of modern cloud and monitoring tools such as Kubernetes, Google Cloud Platform (GCP), and Grafana to ensure a stable and monitored infrastructure.
• Clear improvement in efficiency, scalability, and reliability of the platform, which now meets the demands of a dynamic and growing e-commerce market.