OAuth Experts

Development and further enhancement of an internal quotation system for managing and analyzing insurance policies. The focus was on consolidating existing systems, establishing modern development standards, and improving testing, security, and deployment processes. Alongside implementing new features, special attention was paid to code quality, security, and performance.

Responsibilities:

• Full-stack development of an internal quotation system based on Spring Boot and Angular
• Design and implementation of a secure Spring Security configuration, including certificate management
• Merging two bounded contexts using Domain-Driven Design (DDD)
• Introducing and integrating Testcontainers for automated integration tests
• Establishing and applying common testing methods (unit, integration, and end-to-end tests)
• Presenting and integrating Cypress as a black-box GUI testing tool
• Improving the CI/CD pipeline through automated versioning and a custom Jenkins Library
• Proof of Concept (PoC) for state management with NgRx in the frontend
• Refactoring legacy code and fixing incorrect Spring Boot configurations
• Training developers in Clean Code, best practices, and the Spring Framework
• Developing a tool to analyze test data and improve quality
• Further development of the existing Cucumber project
• Carrying out dependency updates and analyzing and maintaining the application
• Implementing telemetry and building a Dynatrace dashboard
• Improving technical documentation in line with Arc42 and introducing AsyncAPI

Technologies: Scrum, TDD, CleanCode, Spring Boot, Java, Angular, NgRx, Testcontainers, Cypress, Cucumber, Jenkins, Dynatrace, Docker, Git, Maven, Kafka, Oracle, REST, DDD, Arc42, AsyncAPI, IntelliJ, Jira, Confluence, Windows, Linux

Task: Operator development and observability

Technologies and skills: Kubernetes, Valkey-Operator, Crossplane, Backstage, OpenPortal, OTEL, Grafana Cloud, Azure DevOps, Artifactory, Flux, Alloy, Prometheus, Grafana, Loki, OCF, Copilot

What I did:

• Evaluated/developed Valkey-Operator
• Set up OpenTelemetry
• Integrated it with OpenPortal/Backstage/CrossPlane

• Led QA and test automation for a distributed industrial IoT and data-integration platform connecting shop-floor systems with enterprise applications.
• Designed and maintained automated API and UI tests using Playwright, TypeScript, and Python, covering REST APIs, authentication, resource management, integrations, permissions, and end-to-end workflows.
• Tested distributed services, data pipelines, messaging infrastructure, containerized applications, and integrations across Kubernetes, OpenShift, Docker, and Docker Compose environments.
• Performed functional, integration, regression, endurance, resilience, load, chaos, and exploratory testing across complex distributed systems.
• Used Chaos Mesh and Toxiproxy for network fault injection, latency, packet loss, and partition scenarios to validate system resilience and failure handling.
• Automated infrastructure provisioning, configuration, and environment setup with Ansible and managed deployments using Kubernetes and Helm.
• Tested integrations with industrial protocols, messaging systems, databases, HTTP/REST APIs, and external enterprise systems using simulators, emulators, and dedicated test environments.
• Worked with MQTT, Kafka, SQL databases, InfluxDB, REST APIs, OAuth 2.0, JWT, LDAP, Active Directory, OpenLDAP, mTLS, TLS, MFA, SSO, and RBAC.
• Investigated and resolved 40+ defects across backend services, integrations, distributed components, and web applications, using AI-assisted analysis with Claude to accelerate debugging, test design, and root-cause investigation.
• Improved deployment reliability through Kubernetes/OpenShift configuration and health-check tuning and monitored distributed systems using Grafana, Prometheus, and Loki.
• Collaborated with developers and product teams on sprint planning, technical refinement, quality strategy, release testing, and continuous improvement.
• Applied AI-assisted and agentic testing approaches to expand automated coverage and identify complex edge cases.

• Manage multiple Kubernetes clusters in Production with Ceph as storage layer.
• Implemented CICD pipelines for automating deployments with Gitlab CI
• Terraform for Infrastructure provisioning.
• Claude code
• Helm charts for deploying via ArgoCD
• Implemented automated incident notification pipelines in Kubernetes to align with NIS2 mandatory 24-hour early warning disclosure rules
• Configured Azure Policy and Logging guardrails aligned with BSI IT-Grundschutz (SYS.1.3 / OPS.1.1), ensuring continuous baseline compliance across 50+ cloud workloads

Environment: Gitlab CI, IONOS Cloud, Ceph, ArgoCD, terraform, Elastic cluster, Grafana, Alert Manager & Prometheus

Project: Introduction of statutory-compliant electronic invoicing (outbound, Germany) in SAP for an international technology group.

• Project management: Planning, steering and reporting of the E-Invoicing outbound rollout across all affected business areas, including budget and resource coordination.
• UAT: Structured user acceptance test with key users per business area, test cases per invoice scenario, and consolidated test results for decision making.
• Defect management: Handover and tracking of defects in Jira, including validation of the generated invoices against the statutory schemas.
• Cutover, go-live and hypercare: Readiness checks and cutover planning aligned with the statutory deadlines, coordination of go-live and stabilization during hypercare.
• Stakeholder management and reporting: Alignment with Finance, Tax, business departments and IT, preparation of status reports and decision papers, and consistent follow-up of open items.
• Change management and documentation: Communicated process changes to the business departments, enabled key users, and created process and compliance documentation to ensure traceability and audit readiness.

Full overall responsibility: product, technology, compliance and go-to-market

• Delivered an enterprise MVP in 54 days, exceeding scope and schedule.
• Won a 250k € ARR anchor customer and built a sustainable enterprise sales pipeline in the first quarter.
• Paid PoCs with Zalando (35k €) and tesa (26k €), validating product-market fit with Tier-1 enterprise customers.
• Initiated ISO-27001 and TISAX certification processes. Left when the venture entered its next organizational phase.

• Applied modern JavaScript features, including ES6+ syntax, destructuring, modules, array methods, and asynchronous programming, to develop efficient and readable frontend code.
• Implemented frontend integration patterns for PHP and Laravel backend services, connecting React interfaces to REST APIs and handling structured JSON data.
• Developed interactive, functional component-based frontend applications using React Hooks, JavaScript, and TypeScript, alongside backend applications and RESTful APIs using Python, Django, Flask, and FastAPI, focusing on reusable components, modular architecture, maintainability, and efficient data processing.
• Maintained a dynamic portfolio platform using PHP, Laravel, Livewire, and MySQL, implementing end-to-end functionality across frontend interfaces, backend services, and database operations.
• Validated server-side request handling, routing, middleware, and form validation using Laravel features to support reliable application workflows and consistent data processing.
• Designed and managed relational database structures using MySQL and Laravel Eloquent ORM, implementing data models, relationships, database migrations, and efficient queries for content management.
• AI-powered applications integrating Large Language Models (LLMs) through external APIs and locally hosted models, exploring practical use cases for conversational AI, intelligent automation, and AI-assisted workflows.
• Built local AI applications and developer tools for running, configuring, and interacting with locally hosted language models, gaining experience with local inference, model integration, and privacy-conscious AI workflows.
• Explored Retrieval-Augmented Generation (RAG) approaches to combine language models with external knowledge sources, enabling context-aware responses based on relevant application data and retrieved information.
• Integrated AI services with backend APIs and application components, developing reusable modules for model communication, response processing, error handling, and data exchange.

Company in the industrial sector

Projects completed during retraining

• Rebuilt the company website from WordPress using a modern stack with Astro and TypeScript, deployed on Vercel (live at sybarium.vercel.app); replaced the legacy CMS with a faster, maintainable system.
• Reduced page load time by ~80% (from 5 s to under 1 s) through optimization, caching, and asset optimization.
• Developed n8n automation workflows that integrate several REST APIs and internal systems, saving more than 3 hours of manual work per week.

• Co-own the architecture and development of enterprise-grade AI and backend systems spanning communication automation, embedding-based candidate matching and talent-pooling workflows; shape product and feature direction across business, compliance and technical implementation.
• Design and implement production-grade AI pipelines and multi-step LLM workflows, including orchestration, prompt and context engineering, LLM routing and assessment, and integration with internal services and business data.
• Co-own the core candidate-matching system, leveraging vector embeddings and cosine similarity within internal ingestion and attribute-derivation pipelines.
• Drive the architecture and evolution of the candidate-pooling system, including its LLM-based routing and assessment layer.

• 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.

• Built a private second brain: a local AI agent (Ollama) searches my documents using full-text and vector search (RAG).
• Connected it to the Claude app via MCP with its own OAuth server.
• Private content is filtered out in code before a request reaches Claude (privacy by design).
• Development is agentic: AI agents implement user stories, review agents check them, and I accept and merge them.
• Planned for release as open source.

Technologies: Ollama, RAG, vector search, MCP, OAuth, Claude, AI agents

• Contributed to the development of an advanced RAG AI Chat application that integrates multiple LLM models, enabling users to seamlessly switch between models based on specific tasks. This improved the user experience by providing tailored, efficient solutions for various use cases, such as event scheduling, booking systems, and complex task management.
• Participated in designing and implementing a robust backend architecture using Spring AI, enabling advanced AI-driven capabilities like intelligent task automation, language processing, and contextual recommendations. Leveraged Spring AI Tools and Advisors to enhance the performance and decision-making of the AI models.
• Collaborated on the integration of vector databases to support embeddings, enhancing the app's ability to understand user queries and perform actions based on complex, real-time data inputs.
• Contributed to the development of a seamless, user-friendly front-end interface using React with TypeScript support, ensuring a modern, responsive, and scalable user experience across platforms.
• Assisted in implementing state management with Redux RTK for efficient data flow and real-time updates, optimizing the overall user experience in dynamic scenarios such as scheduling and task management.
• Partnered with stakeholders to define feature requirements, helping ensure that the app could scale to meet evolving business needs and integrate with other systems like calendar and email services. Worked alongside cross-functional teams, including data scientists and UI/UX designers, to fine-tune AI models and ensure alignment with project goals.
• Contributed to ensuring end-to-end system performance, security, and compliance by helping integrate authentication mechanisms, role-based access control, and secure communication protocols in both backend and frontend layers.

Technology Stack and Key Contributions:

• Java / Spring Boot / Spring AI: Developed backend services leveraging Spring AI for intelligent responses, task automation, and complex workflows.
• React / TypeScript: Built intuitive user interfaces with React and TypeScript, ensuring a smooth and scalable frontend.
• Redux RTK: Managed application state with Redux RTK for optimized state management, enabling dynamic, real-time data updates.
• Vector Databases: Integrated vector databases (pgVector) for embedding support, improving AI model performance in handling complex queries.
• PostgreSQL / Redis: Managed persistent and temporary data with relational and in-memory data stores, ensuring data integrity and speed.
• Kafka: Utilized Apache Kafka for event-driven communication and seamless integration between microservices.
• Spring Security: Ensured the security of backend services with robust authentication and authorization mechanisms.
• CI/CD & DevOps: Integrated continuous integration and deployment pipelines to ensure rapid and secure deployment of features and updates.

• Complete greenfield rebuild across the whole stack — built AI-native: backend in Go and NestJS, PostgreSQL (CNPG) on K3s with GitOps/Terraform; frontend on Angular 22, zoneless.
• Orchestrated coding agents (e.g. Claude Code, Cursor) across the entire lifecycle — architecture, implementation, testing, reviews, documentation — driven by Specification-Driven Development (SDD).
• “Bruno” — LLM commentator persona backed by RAG and MCP for a personality that stays consistent across all generations (match previews, post-match reports, his own virtual bets).

Angular 22 (zoneless, without Zone.js), Claude Code, Claude Code Skills, CNPG, Cursor, Design Tokens (Spec for Code), Docker, Gherkin, Git, GitLab, GitOps, Go, Google Gemini, Grafana, Hetzner Cloud, K3s, Keycloak, Kubernetes, Lighthouse, LLM Integration, Model Context Protocol (MCP), NestJS, Node.js, NPM, Playwright, PostgreSQL, Prometheus, RAG, REST, Specification-Driven Development (SDD), Structured Outputs, Terraform, TypeScript, Vitest