CV Personal Projects Programming Languages Impressum

Stefan Kölle

Senior Software Developer & Software Architect

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Senior Software Developer / Senior Software Architect

TENHIL GmbH & Co. KG (2025 - present)

• MCP-Server for ChatGPT Integration (2026) Built an MCP server for a major platform integration using Claude Code, from concept to production in 6 half-days solo. Full spec, Confluence documentation, Jira epics and stories, and PO artifacts fully generated within the same workflow.
• AI-driven Project Documentation (2026) Using Claude Code to generate complete project documentation end-to-end, including Confluence pages, Jira epics and stories, covering the full PO process without manual overhead.
• AI-Tooling Repository (2026): Built a structured AI-assisted development framework for the .NET team, providing reusable workflows for plan-and-implement processes, QA testing, and code reviews. Presented at internal Demo Day with full documentation.
• Regular presenter at internal monthly Demo Days, sharing AI tooling advances and new project outcomes with the engineering organization.
• Kubernetes Migration: All microservices are now running on Kubernetes, migrated to self-hosted Kubernetes on AWS machines.
• AI-assisted Development Workflow: Established a production-ready Claude Code workflow for rapid delivery, reducing time-to-production for new services significantly.
• Infrastructure Cost Optimization (2025) Reduced monthly infrastructure costs by €1,850 through strategic decommissioning of legacy systems and cloud routing migration, delivering ~€22,000 in annual savings.
• QA Automation Framework Built a scalable integration test system enabling continuous, code-based QA coverage growth and cross-codebase bug detection across multiple services.
• AI Workshop Organized and led an internal team workshop on AI-assisted search query parsing and natural language processing for job search optimization.
• Active Services Migration to Kubernetes (2025) Planned migration of active production services from legacy hosting to Kubernetes, including documentation and architectural concepts.
• Consistently delivering full-time output while working part-time, recognized across multiple product teams for high productivity and reliable delivery.
• Technologiestack: .NET Core, Kubernetes, Docker, TypeScript, Claude Code, OpenAI, Terraform, Sentry, Loki/Grafana.

TENHIL GmbH & Co. KG (08/2022 - 2024)

• OpenAI Integration (2024) Integrated OpenAI-based salary data generation into a multi-tenant microservice, enabling automated, AI-driven content enrichment at scale.
• Solely responsible for designing and building multiple core backend microservices end-to-end, including application services, geo data, feed generation, salary data, and email delivery integrations.
• Collaborating closely with the Product Owner to create and implement new services.
• Technologies: .NET Core 10, Docker, Azure, Terraform, Uptrends, Sentry, Loki, Quartz.NET.

Senior Software Developer / Senior Software Architect

stellenanzeigen.de GmbH & Co. KG (11/2018 - 07/2022)

• Architecting hosting solutions and migrating services to Azure.
• Implementing a CMS based on Squidex and managing server infrastructure.

Managing Director

Regio-Jobanzeiger GmbH & Co. KG (10/2014 - 12/2017)

Managing Director, CTO

stellenanzeigen.de GmbH & Co. KG (01/2011 - 10/2018)

• Reorganized the company, focusing on performance marketing and core products.
• Implemented the "SmartReach" performance marketing product.
• Significant projects: Multi-brand strategy, founding "Yourfirm" and "Regio Jobanzeiger", integrating "Kalaydo".

CTO, Member of Executive Management

stellenanzeigen.de GmbH & Co. KG (01/2004 - 12/2010)

• Led product management, software development, IT, customer service, and HTML ad creation.
• Introduced agile software development and virtualized all physical servers.

Head of IT / Development

stellenanzeigen.de GmbH & Co. KG (06/2000 - 12/2003)

• Developed a multi-client web frontend and restructured the ad creation process.

Web Developer

IXOS AG (05/1999 - 05/2000)

• Managed web development environment and internal departmental websites.

Education

FH Augsburg - Computer Science (1996 - 1999)

Internships

IXOS AG - Working Student (10/1997 - 04/1999)

• Redesigned the Jukeman website and prepared training rooms for R/3 training.

Personal Projects

moonweb.org (since 2020)

My personal corner on the internet, documenting the homelab, smart home setups, infrastructure experiments, retro hardware, and the code that ties it all together. Everything runs on a homelab that has been evolving since the mid-90s.

• hub.moonweb.org: Overview of all sites and projects.
• infra.moonweb.org: Proxmox cluster, Synology NAS, Docker containers, networking, and backup strategies.
• smarthome.moonweb.org: Home Assistant, MQTT sensors, AirPlay audio, energy monitoring, and ESP32 dashboards.
• code.moonweb.org: Curated catalog of public GitHub projects, sorted by topic.
• retro.moonweb.org: Atari ST, Amiga, DOS, MiSTer FPGA, and the retro computing corner.

Home Network Projects (2025-2026)

• Docker Host (Proxmox PVE)
  Virtualized Docker host with Debian 12.2 running containerized services including Portainer, Prometheus, Grafana, Gitea, monitoring exporters, and more. Full architecture documented on infra.moonweb.org.
• InfluxDB Time-Series Integration
  Deployed InfluxDB 2.x for sensor data collection from Tasmota smart plugs and HomematicIP thermostats, replacing older MySQL-based storage with modern time-series architecture.
• LED Matrix ESP32 InfluxDB Integration
  Data persistence layer for LED Matrix ESP32 sensor systems (DHT22 temperature/humidity) with InfluxDB 2.x backend. Automated collection at 60-second intervals for historical trend analysis.
• Air Quality Dashboard
  Dynamic HTML5 dashboard consuming real-time sensor data from InfluxDB via Flux query API. Displays temperature and humidity across all network locations, accessible via nginx reverse proxy. See also smarthome.moonweb.org.
• Tasmota Energy Monitoring
  Smart plug energy tracking with 8 Tasmota-enabled devices, integrating MQTT data collection and visualization. See also smarthome.moonweb.org.
• Network Hardware & Monitoring
  Four Zyxel GS1200-8HP managed switches in the server room, living room, and study, plus a Multi-WAN OpenWrt router for failover and VLAN segmentation. All switches feed into Prometheus monitoring via SNMP exporters, and IoT devices are isolated in VLAN 189.

Retro Computing (2022/2023)

• MiSTer and MiST FPGA Systems for preservation (see also retro.moonweb.org).
• DOS System, Amiga System, and Atari ST System with the environment from the early 90s.

Upgrade of old Atari Mega 4 (2021)

• Gotek Drive
• More RAM
• Alternative TOS ROMs
• SD HDD Adapter

Home Automation (since 2018)

• LED Matrix ESP32 for date, time, weather, and status messages via Web API, with a display in every room.
• MQTT for message transfer and remote control via Tasmota RF modules (433MHz).
• Power meter monitoring for washing machine and tumbler with info messages on LED matrices when finished.
• MP3 player with automated playback (e.g., bathroom radio when light is on).
• Raspberry Pi with pilight and RF433 module for remote control power plugs.

Various Docker Systems (since 2016)

• Monitoring: Prometheus, Grafana, InfluxDB, cAdvisor, Node Exporter, SNMP exporters
• Smart Home: Mosquitto MQTT broker, Home Assistant
• Infrastructure: Portainer, Nginx Proxy Manager, Authelia (SSO), Watchtower, Healthchecks
• Applications: Gitea (GitHub mirror), Stirling PDF, TubeArchivist, TubeSync, SearXNG

Walk-on Song (2019)

• When someone enters the office, their jingle is played.
• ESP32 scans WiFi, if a known device is found for the first time per day, the jingle is played.
• MP3 Module for playback on attached speaker.

Kids RFID MP3 Player (2018)

• Interactive audio playback system utilizing RFID technology.
• Powered by an Arduino Nano for compact and efficient operation.
• Plays specific audio files when RFID-tagged objects or cards are placed on the device.
• Customizable: users can upload and assign personalized audio content to RFID tags.

.NET Community Activity (2009 - 2011)

• Attended multiple .NET Open Spaces, including Ulm 2009 and Leipzig 2009.
• Developed a schema-less object storage system named StupidDB.
• Contributed to a developer blog with colleagues.
• Actively participated in Coding Dojos at AutoScout24.

Owner & Developer, inseco.de (2003 - 2008)

• Managed approximately 20 clients, primarily from the gastronomy and club sectors.
• Developed a CMS system for maintaining their websites, programmed in PHP and MySQL.
• Included modules for photo galleries, menus, and events.

Home Network Projects during IT Manager Phase (2000 - 2006)

• Set up a home network with various Linux servers and Windows NT 4.0.
• Implemented a predecessor to the pfSense firewall.
• Managed a FreeBSD server with Apache, Sendmail, and Perl scripts.
• Maintained an NT 4.0 file server.
• Administered Windows 98 and Windows 2000 hosts.
• More info at moonweb.org/network/

Mailbox/Fidonet (1994 - 2000)

• Operated a BBS and Fidonet Node (see also FidoNet Nodelist on 28k8.moonweb.org).
• Managed a node in Augsburg with an uplink directly to the NC in Munich.
• Software was running on an OS/2 computer.
• Utilized 2x ISDN and 1x MODEM connections.
• Had about 20 subnodes and points.
• Served as the Bavaria HUB/HOST for various old networks.
• Developed several small software tools in Turbo Pascal for DOS.

PC Intro / Game / Software Development (1992 - 1994)

• Released Phobia Welcome Intro (Sourcecode/Picture/Video) for 486 PC in 1994.
• Released Tr@anceMission Intros (Sourcecode/Pictures/Videos) in 1992 and 1993.
• Developed Turbo Pascal Graphics Library X-Lib Unit (Sourcecode).
• Used Turbo Pascal and inline assembler for development.

Atari ST Software Development (1990 - 1992)

• Completed game 'Atom oh no' in 1992 (GFA Basic)

Programming Languages

AI-Assisted Development

I've fully embraced the AI-assisted development paradigm since early 2025. At work, I've taught Claude Code a workflow for handling Jira stories end-to-end: it evaluates requirements, provides feedback to the PO, and creates a detailed implementation plan. From there, it's mostly about supervising the plan while the code generation runs largely autonomously. For code review, we use a second AI (e.g., Codex) as a quality gate to catch issues that might slip through. In migration projects, I define the exact plan upfront and Claude Code executes it with increasing independence. The output gain is massive, delivering in a fraction of the time.

Privately, I work with OpenCode paired with OpenCode Zen, Merge Gateway, and OpenRouter, mostly for Python-based home lab and automation projects. See my GitHub projects for examples and the Dev VM setup for the infrastructure behind this workflow.

.NET Core

• Working with .NET Core since 2018 at stellenanzeigen.de GmbH & Co. KG, which became TENHIL GmbH & Co. KG in 2022, where I migrated the old VB and ASP-Classic applications to modern .NET Core.
• Built around a dozen microservices, including Jobs Per Mail, JobApply, GeoService, Feedexporter, and Salary Data Service, first hosted on Azure and built with Docker, Terraform, Azure Tables, Azure Blobs, S3 buckets, and PostgreSQL.
• Since this year, all of these microservices run in our self-hosted Kubernetes cluster on AWS machines.
• Introduced Squidex as a headless CMS for the microservice backend, with Sentry and Loki for monitoring and logging, and Quartz.NET, later Hangfire.NET, for scheduled jobs.

TypeScript

• Using Node.js privately for over a decade, TypeScript since its early days, and professionally at TENHIL since 2024.
• Since this year, TypeScript is my go-to for AI-built microservices.
• Built an MCP (Model Context Protocol) server for ChatGPT integration in 6 half-days using Claude Code.
• Implemented a TypeScript widget renderer for AI-driven applications with the OpenAI Chat Kit.

Python

• Working with Python since 2020 on private projects, home lab tooling, and automation scripts.
• Since this year, increasingly using Python for home network projects, with development accelerated by AI-assisted workflows in OpenCode.

.NET Framework

• As CTO at stellenanzeigen.de GmbH & Co. KG (2004-2010), drove the move from ASP Classic to the .NET Framework, replacing the monolithic setup with a layered architecture of SOAP web services.
• Hosted applications on Windows IIS with MSSQL as the database.
• Introduced TDD and DDD practices and shared that knowledge with the .NET community at OpenSpaces and CodingDojos.

PHP

• Developed a website CMS system (activetool.de) for multiple clients from 2003 to 2008.
• Created a PHP Ticketing System and worked with MySQL databases.

ASP-Classic

• Started with ASP-Classic on PC (Windows) in 1999 while working as a web developer at IXOS AG: managed the web development environment and built internal departmental websites, introduced search functions, request systems, and link checkers to optimize web servers, developed a Visual Basic application for generating static web pages, and designed a workflow for maintaining the website using ASP scripts and SQL databases.
• Led the IT and development department at stellenanzeigen.de GmbH & Co. KG from 2000 to 2003, migrating applications from idc/htx to ASP-Classic and developing a multi-client web frontend for newspaper publishers.

Java

• Began using Java on PC (Windows) in 1998.
• Participated in a Security Hash Team Project at iXOS Software AG, developing the Java frontend.
• Utilized development environments such as Kawa and IBM Visual Age.

C++

• First used C++ on PC (Windows) in 1997.
• Worked on an R/3 Integration Project during practical work at iXOS Software AG.
• Completed one semester of C++ on UNIX (Solaris) during studies in 1998.

PASCAL

• Started with PASCAL on PC in 1993, using TurboPascal 6.0, 7.0, and Borland Pascal 7.0.
• Developed DOSMENU, a menu system for DOS, and tools for Fidonet.
• Created two games: a Wheel of Fortune clone and a two-player Tetris.
• Studied PASCAL for one year in school (1994) and one semester on UNIX (Solaris) during studies in 1996.

Assembler

• Began learning Assembler on the Atari ST in 1992, creating simple programs with Pure Assembler, part of the Pure C Pack.
• Developed a small text mode demo with sound using DevPAK.
• Gained experience on PC in 1994, creating four demos using inline assembler in TurboPascal.

C

• First encountered C on the Atari ST in 1992, creating simple programs with Pure C, an advanced version of Turbo C.
• Completed one semester of C during studies in 1997.

BASIC

• Gained initial experience with BASIC on the EPSON HX-20 in 1988 and Atari ST in 1989.
• Developed two small games (Bowling, LiveStyleCity) using OmicronBasic.
• Created games such as AtomOhNo (an Atomix clone) and TOPchangethecolor with GFA-Basic and TOPpack.
• Produced graphic demos on the Atari ST around 1991.
• Developed simple programs using Amiga Basic in 1991.
• Studied BASIC for two years in school (1991-1992), including coding a Snake clone during class.

Legal Notice (Impressum, § 5 DDG)

Stefan Kölle
Neumarkter Str. 86c
81673 München

Phone/Fax: +49-(89)-20006547
E-Mail: [email protected]

Responsible for content according to § 18 (2) MStV: Stefan Kölle, address as above.

Full legal notice & privacy policy for this website and the moonweb.org network: hub.moonweb.org/impressum