Stripe Expert

Stabilization of a critical logistics outsourcing setup in the context of an SAP S/4HANA transformation. The focus was on restoring a reliable operational fact base between the client, logistics service provider, international supplier plants and the SAP/IT organization.

• Coordination between the client, global logistics service provider, international supplier plants, SAP/IT teams, Quality Management and the operational shop floor.
• Management, monitoring and operational correction of Inbound Deliveries; integration of Outbound Delivery processes.
• Analysis of interface, posting, batch and master data errors between SAP S/4HANA, logistics service provider, supplier plants and internal business functions.
• Significant reduction of critical inventory differences between the client and logistics service provider.
• Improved operational management capability in the logistics environment and creation of a common fact base.
• Reduction of recurring error patterns in the areas of Inbound Deliveries, inventory, interfaces, batch/posting logic and service provider processes.

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.

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

Development and further development of an internal platform for managing and providing technical resources, virtual machines, and infrastructure services. The platform supports self-service processes and covers functions that are conceptually comparable to cloud management solutions like Azure or AWS.

• Responsible involvement in the design, development, and implementation of new backend and frontend features
• Hands-on development with Java, Spring Boot, Python, and Angular
• Implementation of REST interfaces, business logic, validations, and integrations into existing system landscapes
• Further development of modern web interfaces with Angular, including connection to backend services
• Participation in architecture and design decisions within the team, especially with regard to scalability, maintainability, and clean interfaces
• Containerization and deployment of applications with Docker, Kubernetes, and Helm
• Support with CI/CD processes and deployment to Kubernetes-based environments
• Work in the environment of vSphere, Broadcom, GitLab CI/CD, ArgoCD, Maven, npm, and NuGet
• Close collaboration with developers, business teams, DevOps, and other technical stakeholders
• Analysis of technical requirements, deriving suitable solutions, and independent implementation in an agile team
• Use of GitHub Copilot to support code generation, refactoring, test case creation, and technical documentation

Methods/ tools/ technologies: Languages & frameworks: Java (21), Spring Boot (4.x), Python, Angular, Robot Framework, Kubernetes, Helm Persistence: PostgreSQL, MongoDB, Hibernate, Liquibase Architecture & communication: REST, gRPC, GraphQL, Apache Kafka, OpenAPI, Microservices, Event Driven, Domain Driven Design Cloud & infrastructure: Terraform, Docker, Rancher, Helm, Ansible Security: OAuth2, MS (Entra ID), web security, Keycloak (extensions for detailed group rights) DevOps: GitLab CI/CD, Ansible, Maven, Gradle, Grafana, Prometheus, Git, GitHub Copilot Testing & QM: JUnit, Robot Framework, automated component and integration tests, E2E tests with Playwright, Testcontainers, EasyMock Methodology & approach: Kanban, JIRA, Confluence, Clean Code

Enterprise Agile Planning Platform

Key achievements:

• Introduced and promoted shift-left testing practices.
• Established and maintained QA metrics to track release quality and support data-driven decision-making.
• Reviewed Selenium-based automated tests, identifying coverage gaps and prioritizing improvements with the automation team.

Responsibilities:

• Managed QA activities throughout the release lifecycle, coordinating testing efforts and ensuring release readiness.
• Mentored and onboarded 10 QA engineers and fostered knowledge sharing.
• Conducted technical interviews and participated in candidate evaluation.
• Collaborated with stakeholders to improve quality practices.

• 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

Further development of a software solution for managing audit applications and audit notifications according to §106d SGB V for the Association of Statutory Health Insurance Physicians in Hamburg.

• Developed numerous features, optimised performance, refactored code and analysed errors
• Refactored the development container setup
• Optimised the Gitlab-CI build pipeline
• Introduced improvements to the team workflow

• Lead Product Owner role for the BFSG pilot journey “Search and Book” across web and app, focusing on digital accessibility, UX, conversion, and regulatory implementation.
• Created and prioritized the product backlog; derived user stories and acceptance criteria from legal standards (BFSG, WCAG 2.1)
• Developed a product vision that combines digital accessibility, user-centered UX, and conversion optimization for the booking journey
• Cross-stream release management and quality assurance across the entire web and app area, including go/no-go decisions, rollout, and user acceptance tests
• Coordinated and prioritized with Legal, Compliance, external BFSG consultants, UX, Development, Marketing, and Management
• Conducted user research as well as usability and accessibility tests (including screen readers and keyboard navigation) and prototyping with UX/UI
• Defined KPIs to measure accessibility, conversion, and user guidance
• BFSG pilot journey “Search and Book” successfully delivered: first accessible features rolled out and the foundation for a long-term BFSG-compliant booking journey established
• Established sustainable process integration through close collaboration with consulting partners and internal teams

Designed and developed an Azure-based AI and data platform transforming distributed project documents into searchable, structured knowledge for an enterprise AI assistant. Combined incremental document processing, hybrid keyword/vector retrieval, knowledge graph extraction, and conversational AI for Microsoft Teams and Microsoft 365 Copilot. Implemented Python document-processing pipelines for PDF, Word, Outlook and text files; Azure Cosmos DB lifecycle management; Azure AI Search; Azure AI Foundry and Azure OpenAI; identity-aware retrieval with Microsoft Entra ID; project authorization; a TypeScript Microsoft Agents SDK agent; Pulumi infrastructure; resilient scheduling, retry and diagnostic tooling. Technology stack: Python, TypeScript, FastAPI, Pydantic, Azure AI Foundry, Azure OpenAI, Azure AI Search, Azure Cosmos DB, Blob/Table Storage, Container Apps/Jobs, Service Bus, Key Vault, Entra ID, Docker, Pulumi, pytest, Microsoft Teams and Microsoft 365 Copilot.

Co-founded a software agency building custom web and cross-platform products. I owned the technical decisions across the whole portfolio and led 12 people, while carrying delivery planning, process and client relationships for 11 clients across 3 industries.

• Technical leadership: owned the technical decisions for the codebase across every project — stack, architecture, code conventions and the tooling the team worked with — and led the developers on how work got built through code reviews, pair programming and mentoring across a team ranging from junior to senior, keeping the codebase coherent as the portfolio and the team grew

• Delivery planning against the financial plan: built the company's financial plan and derived from it the billable hours each developer had to reach per month and the hours each project could absorb to stay within budget; planned capacity and scope against those figures and negotiated budgets and delivery dates directly with clients

• Client ownership: technical contact across the portfolio — requirements gathering and prioritisation, scoping and estimates, timeline communication, budget negotiation, and consistent transparency throughout delivery

• Team and people: owned the hiring and interview process end to end and took responsibility for offboarding where it was needed; designed an onboarding that got new developers productive within 1–2 days; cleared blockers daily and kept a close eye on where effort was creating value and where it was not

• Process ownership: consolidated a micro-service landscape spread over 15+ repositories into a single monorepo, cutting backend development time by ~40% and simplifying releases for 6 engineers; set up deployment pipelines with GitHub Actions and GitLab CI; ran retrospectives and turned the feedback into concrete changes; introduced AI agents into day-to-day development

• Delivered short-staffed: when the team shrank from 8 developers to 2, restructured scope, introduced AI-assisted development to hold the schedule and took on Go backend work alongside my own frontend scope

• Architecture and code: defined the architecture for every project in the portfolio — the structure the rest of the team built within — and wrote roughly 90% of the frontend code myself, from SSR applications with Next.js and Remix to cross-platform apps with Capacitor

• From zero to production: took a practice management platform — administration, inventory, integrated online shop, chat messenger — from an empty repository to production. Live in 7 markets with at least 7 more coming up, serving tens of thousands of users

• Delivery under pressure: built and shipped a replacement online shop for a Fortune 250 client in 4 days, restoring order intake while their global shops had been offline for several weeks

• Design system: built a cross-project design system used across 7 products, so new projects and features started from a shared, consistent base

• Cross-platform and real-time: built iOS and Android apps with Capacitor for a client live event with 1,000+ participants — web sockets and push notifications for real-time content, Stripe payments supporting PayPal, Apple Pay, Google Pay and cards

Key technologies: React, TypeScript, Next.js, Remix, GraphQL, ConnectRPC, Redux, Zustand, Go, Node.js, Turborepo, Nx, Capacitor, Ionic, WebSockets, Stripe, PostgreSQL, Playwright, Cypress, Vitest, Storybook, GitHub Actions, GitLab CI, Claude Code, Cursor, GitHub Copilot

· Initial situation and target picture – which problem does the platform solve, for which user group? · Requirements gathering and scope – from the idea through the processes to the scope, · Architecture and technology selection – stack, hosting, data storage,

• Vercel Inc. – hosting and delivery of the application.
• Supabase – database, authentication, and file storage.
• Stripe – processing payments for application and unlock fees.
• Resend – sending transactional notification emails
• Calendly – appointment booking for consultation calls; processes the data provided there (e.g. name, email address, appointment request). · AI components – which models or providers, which task does the AI take on exactly,
• Claude Opus 5 by Anthropic. · Data model and integrations – interfaces to third-party systems, import/export, APIs.

• TrendReel, production LLM agent and RAG system (Python, LangChain, OpenAI, Groq/Llama 3, Claude, FastAPI, Kubernetes, PostgreSQL).
• Designed and built a production multi-step LLM agent system: a script generation agent with a per-platform psychology database, 7 viral narrative frameworks, and structured quality scoring, switching between Claude and Groq backends in real time based on output metrics.
• Implemented multi-provider LLM routing (Claude primary, Groq/Llama 3 fallback) with priority-chain failover and quality-based provider switching, achieving 95% inference cost reduction while holding measurable quality thresholds.
• Built an advanced RAG-style retrieval pipeline with per-platform knowledge bases, semantic content matching, and structured output evaluation across 7 decision frameworks, directly analogous to multi-tenant context-based reasoning for enterprise document workflows.
• BrainyAI, adaptive AI learning platform (Python, LangChain, Groq Llama 3.3-70B, OpenAI, Next.js, Supabase, Redis).
• Integrated Groq Llama 3.3-70B with education-level-aware prompting, dynamically adjusting vocabulary depth, citation complexity, and reasoning style across four student proficiency tiers.
• Nexus Prime, multi-tenant SaaS platform for marketing and growth automation (25 modules, 99 backend routers, 153 frontend files).
• Built a 25-module, 99-router multi-tenant SaaS platform covering ad remix, affiliates, WhatsApp inbox, email, and cart recovery, serving four subscription tiers from $199 to $1,999 per month with integrated Stripe, Paystack, and Flutterwave billing.
• AI Video Surveillance Platform, multi-tenant edge and cloud computer vision system currently in active client pitch.
• Designed a multi-tenant AI video surveillance platform combining edge YOLO26 inference on NVIDIA Jetson Orin NX boxes with a central GKE cloud layer (Postgres, Pub/Sub, ClickHouse, R2, Keycloak) for event storage, dashboards, alerting, and multi-tenancy.

Led FP&A tech transformation for a 9-figure business – from resolving legacy technical debt to leading AI-native EPM implementation

• Driving end-to-end FP&A transformation, from architecture redesign through EPM tool selection to rollout
• Ran evaluation of 12+ EPM platforms, from vendor negotiation to selection framework tied to long-term planning
• Diagnosed constraints in financial planning architecture, presented findings to the CFO, and secured executive mandate to redesign FP&A infrastructure from the ground up

• Self-employed · Berlin, Germany
• Co-founded the company and own the entire technical side: product architecture, backend, frontend, infrastructure and operations.
• Designed and built the Automated Booking System (ABS) as well as the core platform and payment logic.
• Development of AI-powered SaaS products, from architecture through backend and frontend to production operation.
• Technical consulting on product architecture, data protection and permissible automation.
• Building, running and monetising my own API products for AI agents, each available as a REST interface and as an MCP server.
• Full ownership of architecture, infrastructure, billing, legal texts and go-to-market.