React Experts

Evidence-led health intelligence platform turning published research into personal health protocols. It scores 430 habits, foods, and supplements against the studies behind them, and moves the score when the evidence moves. Built solo.

• Built the daily ingestion pipeline across PubMed, bioRxiv, and medRxiv: 43,000+ papers from 3,400+ journals processed into 230,000+ typed evidence claims, each one traceable back to the study it came from.
• Designed the six-factor evidence scoring model and the public changelog behind it, so no recommendation ever appears without the papers underneath it. 23,000+ grade changes recorded and explained to date.
• Shipped an entity information model connecting every intervention to its mechanisms, biomarkers, and outcomes: 118 biomarkers with region-specific reference ranges, 77 mechanisms, 32 graded outcomes.
• Built the personalisation layer: blood panel ingestion that reads lab PDFs with a vision model and corrects results for draw time against the user's wake anchor, plus Oura, WHOOP, and Withings integration for daily readiness context.
• Operate eleven specialised review agents over the corpus and codebase, covering paper curation, retrieval quality, health-claim compliance across EU and US regimes, and security.
• Shipped the Evidence Assistant, a RAG assistant that answers from the claim database and cites the underlying papers, plus a B2B practitioner tier, an Expo React Native app, and localisation across 3 languages and 7 markets.

Stack: Next.js 16, TypeScript, Supabase, pgvector, Anthropic Claude, Vercel, DeepInfra.

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 a custom MediaWiki instance including installation, MySQL database, SSL, and automatic backups
• Set up user roles (Admin, Mod, Verified, User) and a permissions system
• FlaggedRevisions for editorial review workflow · comment and rating extensions

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

• Planned and developed a CPU monitoring application for monitoring system performance and resource utilization.
• Designed and implemented a Spring Boot backend providing a REST API for processing and exposing monitoring data.
• Developed the React frontend for presenting monitoring information in a clear and user-friendly interface.
• Integrated PostgreSQL for persistent storage and management of application data.
• Containerized the application and its services using Docker Compose.
• Automated infrastructure provisioning and deployment using Terraform on AWS.
• Structured the application as a modern, maintainable system using REST-based communication between frontend and backend.
• Designed and developed a secure, scalable CPU monitoring architecture (cpu-watcher) with a dedicated collector application that streams monitoring data to the backend, reducing direct exposure of system resources.
• Designed a secure cloud infrastructure with the database isolated within a private network and OIDC-based authentication.
• Implemented Infrastructure as Code with Terraform and integrated version-controlled CI/CD pipelines to automate testing, infrastructure changes, and application deployments.
• Designed and implemented the frontend delivery architecture using AWS CloudFront.

Stack: Spring Boot · React · PostgreSQL · REST API · Docker Compose · Terraform · AWS

• 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.

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

• 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

• After several S/4 go-lives, structure, role clarity, and decision clarity were missing in Finance and IT; governance mechanisms, prioritization logic, and responsibilities were not defined well enough.

• Unclear interfaces, high coordination effort, and inconsistent ways of working led to organizational instability and limited leadership and steering capability.

• The existing operating model between Finance, Controlling, and IT was not working, which affected transparency, collaboration, and decision paths.

• Designed the transformation and organization architecture for Finance and clarified roles, decision paths, and priorities.

• Diagnosed and structured the Finance and IT organizations (DE/UK/PL), including collaboration, responsibilities, and interfaces.

• Redesigned the Finance–IT operating model with a focus on governance, steering routines, and cross-functional collaboration.

• Enabled leaders and teams, especially Global Process Owners, Key Users, and Finance Leads (systemic organizational development / leadership).

• Steered the transformation portfolio, including clarity on risks, dependencies, and cross-functional decision processes.

• Restored structural steering capability by clearly defining roles, decision paths, and priorities and anchoring them across the organization.

• Strengthened governance and cross-functional collaboration in a systemic way - Finance, Controlling, and IT worked again in consistent, aligned structures; friction losses dropped measurably.

• Harmonized working and communication logic, making coordination faster, more transparent, and less conflict-heavy.

• Enabled the organization in a sustainable way, including the build-up of a strong Key User / Process Owner community and clearly defined steering routines.

• Made the transformation structurally manageable - prioritized initiatives, clear risk and progress logic, and consistent decision formats increased execution speed.

• Building a data integration platform for high, medium, and low voltage assets for contextual analysis of time series with master data from the SCADA control system (IEC 60870 104), INIS, and SAP.
• Responsibility for the architecture and implementation of the solution, as well as sparring partner for the Product Owner.
• Use of Kotlin, Spring Boot, Maven, TimescaleDB, PostgreSQL, liquibase, Elements IoT, Docker, Kubernetes, Grafana, Python, jupyter, and various API gateways.

• LLM-based features for automated CO₂e data extraction from unstructured documents (70% reduction)

• Agentic AI pipeline for automated Scope 3 emissions calculation with 150,000+ validated data records

• Smart API workflows for real-time carbon footprint calculations in ERP and ESG systems

• ML algorithms to predict emission hotspots and optimize product design

• Automated data validation pipelines with NLP for quality assurance of CO₂e datasets

• Led a 15-person cross-functional team to develop 10+ AI features

• Strategic product planning and AI roadmap with 35% shorter time to market

• Stakeholder management with DAX companies (40% higher satisfaction, 95% retention)

• On-time project delivery with 95% budget adherence through data-driven backlog management

• Agile methods (Scrum, Kanban) with continuous AI/ML integration (25% team velocity increase)

• Product-market fit for AI features through A/B testing and analytics (60% higher adoption rate)

• Development of scalable backend applications with C#/.NET and Java
• Design and implementation of distributed microservice architectures
• Development and integration of REST APIs for industrial applications
• Development of modern web applications with React, Angular, and TypeScript
• Implementation of MQTT-based communication solutions
• Integration of industrial protocols such as OPC UA and Modbus TCP
• Development of batch, process control, and HMI components
• Containerization and deployment of applications with Docker
• Conducting code reviews and supporting architecture decisions
• Close collaboration with product owners, QA, and interdisciplinary teams
• Analysis of business requirements and implementation of technical solutions
• Further development of existing software architectures with a focus on maintainability and performance

Technologies: C#, .NET, ASP.NET Core, Java, C++, React, Angular, TypeScript, Vue.JS, MQTT, OPC UA, Modbus TCP, Docker, GitLab, MariaDB, MySQL, Linux