Building software products with AI.as an AI Architect

20 years of engineering in business- and safety-critical systems – E.ON Energy Trading, SonarSource, Stadtwerke München, care IoT. Since February 2026 he has orchestrated Claude Code in TypeScript, Rust and Bash instead of writing production code by hand – and takes teams through the same leap.

Strong communicatorCreativePositive

What you hire him for

Twenty years in one picture

Career stations 2004–2026. Click to open a station in the conversation.

sustainable architecture decisions, […] creative facilitation techniques

A team lead at a public-transport operator, reference letter 2022

Career

Teams he is proud to have been part of. Details unfold – or the assistant shows them to you.

since 2024

AI Architect · Principal Developer

uCORE Systems · Fraunhofer spin-off, research – IoT system for care facilities

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Since 26 February 2026 no more production code by hand – Claude Code introduced in the project on his own initiative and orchestrated since. Hands-on backend and edge development of an IoT system for care facilities. Shaping the flow of information across all technological boundaries (IoT, cloud, UI). Advising on IT security and development processes including testing.

proposed Claude Code in a retrospective; processes switched within two weeks (GitHub issues as the agent’s backlog)
Introduced Claude Code in the project; migrated 15–20 microservices to Rust; embedded work on Raspberry Pi CM5
Advised on IT security and development processes (incl. testing)
“The documentation is the code”: behaviour as a state matrix with behaviour-driven tests (sensor input → actuator output) – even management can specify behaviour
Designed the information flow across all technological boundaries (IoT, cloud, UI)
Hands-on backend/edge development of an IoT system for care facilities
rebuilt the edge controller: from Java 5/Karaf with countless vulnerable dependencies via Docker, Python and TypeScript/Node to Rust – Docker eventually removed again
Buildroot instead of Raspberry Pi OS: lean custom Linux, read-only file system, SBOM, hardening; logs only in RAM, stored encrypted

“… exceptionally broad and deep software-engineering know-how …, covering classic embedded and legacy technologies as naturally as modern, state-of-the-art approaches and architectures …”

Management of an IoT provider for care facilities, employment reference 2025

2022 – 2024

Head Coach Java · technical lead Java, AWS/Cloud, full stack

Coding bootcamp for career changers · teaching and department lead, Hamburg – 100 % remote

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Two years of teaching and leadership, not attendance: technical lead of the Java, AWS/Cloud, full-stack and first-level-support areas, interim line management of the Java and AWS/Cloud departments; technical lead of the company’s most important international upskilling projects. From 2022, integration of AI into course-material production and course material on AI-assisted software development. Responsible for the Java–React curriculum, trained around 150 career changers, talks and public outreach in Germany and Switzerland.

Led the Java and AWS/Cloud departments (interim, line management)
Teaching material on AI-assisted software development (documented in the reference)
reworked and normalised the curriculum with ChatGPT – teachers interchangeable, defined day by day; German in Git, CI translates automatically
brought junior coaches from earlier courses to the point of running courses themselves
with the sales team in customer meetings: won and delivered the largest B2B contracts
Technical lead of the most important international upskilling projects
Talks, public outreach and ownership of the Java–React curriculum
shaped didactics across all areas – comprehensibility after Schulz von Thun as a guiding principle; teaching videos, Twitch podcast

“Internationally experienced, with outstanding developer skills …”

Former department head at a developer bootcamp, reference letter 2023

2014 – 2016 · 2018 – 2022

Lead Developer & Team Coach

Stadtwerke München · emergency call centre and control of Munich's traffic lights (MVG)

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Software for the emergency call centre and for controlling Munich's traffic lights – safety-critical, in continuous operation. Facilitated Scrum meetings, usability sessions, design meetings, pair and mob programming. Trainer and coach for the team.

Facilitated Scrum meetings, usability sessions, design meetings, pair/mob programming
Trainer and team coach; knowledge transfer as a core task
Software for the emergency call centre and Munich's traffic-light control
SAP interface from up to an hour down to 50 ms: own cache with REST access, used by many departments
conceived a map visualisation on his own initiative: three years of GPS data of all vehicles, jump to any second in 2–3 seconds, down to a single vehicle in 3D (WebGL, Mapbox; domain-compressed JSON in MS SQL)
route shapes from GPS traces: computing time for 24 hours of data from a full day down to about a minute on a desktop PC – basis for congestion analysis and the drivers’ navigation devices
equipment database: unique IDs across all workshops – radios, counting systems, cameras, every service vehicle; generically extensible (GWT, Java EE, Jenkins)
built the control centre’s audit-proof incident documentation (Angular, Spring Boot); later made it fast again with index structures

“… sustainable architecture decisions, […] creative facilitation techniques …”

A team lead at a public-transport operator, reference letter 2022

2017

Java Developer

SonarSource, Geneva · maker of SonarQube and SonarCloud

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Development of the open-source tool SonarQube for code quality and security. Building the SaaS offering SonarCloud and implementing its worldwide search. Scaling in an environment of one billion Docker downloads.

Development of SonarQube (open source, code quality and security)
Building SonarCloud, implementing the worldwide search
Scaling and DevOps in an environment of one billion Docker downloads
back-end platform team: database migrations, back-end APIs for plugins and front end, multi-tenancy for the cloud edition
hardly any dependencies, minimalist frameworks, code reviews – one of the founders as mentor

“… motivation, calm, persuasiveness and a positive attitude …”

Executive at a code-analysis software vendor, reference letter 2017

2009 – 2016

Java Developer & IT Supervisor

Pension fund · insurance company – external, part-time, reporting directly to management

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Advice on technology decisions, IT security and software development processes. Led migration projects and development: SEPA migration, Delphi-to-Java migration, introduction of version control. Led and coached the five-person IT team as an external – introduced agile practices, trainings and lecture series for the whole company.

Advice on technology decisions, IT security and development processes
Coached the five-person IT team: introduced daily stand-ups, Scrum boards and Kanban, trainings (from new tools to Excel tricks for the clerks) and lecture series for the whole company – brought a mixed team to one table
Led migration projects (SEPA, Delphi → Java, VCS introduction)
IT responsibility as an external: weekly alignment, JIRA and Confluence for the whole company, introduced version control (Visual SourceSafe → Subversion)
migrated the actuarial core from Delphi to Java (TDD, actuarial maths: mortality tables, technical business plans); SEPA account management as a microservice; renewed the online tariff calculator
first assignment under time pressure: tax-ID report uploaded just before midnight, contractual penalties averted

“… on technology decisions and personnel matters […] [we] trust his judgement …”

Board member of a pension fund, reference letter 2016

2008 – 2016

Lead developer & consultant – energy trading, automotive, medical technology

Projects through the family business · Schwarz System Consulting GmbH · E.ON Energy Trading, a Bavarian car maker, laser and medical-device manufacturers, healthcare

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Business-critical systems, among them the energy-trading platform “Neon” at E.ON Energy Trading. Consulting and coaching on development processes and agile transformations. User interfaces for laser systems in research, medicine and industry; software distribution in the automotive industry; new product development in healthcare.

Energy-trading platform at E.ON Energy Trading (Java, Oracle)
Responsible for his own budget, acquired and served clients himself
Consulting and coaching on development processes and agile transformations
Java/Swing user interfaces for laser systems (excimer, ophthalmic and industrial lasers) and an EMS medical device: maintenance workflows for technicians with working and target states, abort and recovery paths, RS232 to PIC microcontrollers, configurable laser bursts; the devices shipped in small series with these interfaces
E.ON: system reporting grid loads and power volumes to European grid operators – new GWT front end for the traders, redundant production system, time zones as a constant topic
E.ON: knowledge transfer during the move to Düsseldorf – the work of two developers was continued by an offshore team of five to six
automotive: build migration Ant → Maven with byte-identical artefacts; software distribution to workshops (first Scrum project there, TDD, upload integrity via hashing)
greenfield learning platform for the care sector (GWT): shaped data model and documentation; when behind schedule, cut a little-used feature – “nobody missed it”
Audio analysis software (2015, in-house): assessing complete transmission chains (filter, amplifier, loudspeaker, microphone) on real waveforms – signal sent to the function generator and response of the triggered oscilloscope compared via SCPI, single frames and measurement series, instead of just THD or frequency sweeps

“… an absolute Java genius …”

A project manager in energy trading, reference letter 2010

2004 – 2008

Trainee, later Junior Developer

AXA · joined DBV Winterthur, acquired by AXA during his employment

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Development of the authentication service in the “Client-Server Architecture” department. Mentoring of apprentices. Dual vocational training as application developer (IHK).

Authentication service in the “Client-Server Architecture” department
Mentoring of apprentices
Vocational training as application developer (IHK, 2006)
maintained and extended the access-rights portal for external users (agencies, brokers)
final project: additional authentication via a randomly generated code sent by post – 100 out of 100 points
theory at the CSC Deutschland Akademie: small group, project management, presenting – taught the Java block there himself

“… independent, conscientious and precise … high reliability and care …”

Employment reference from an insurer, 2008

1991 – 2004

Coding mentor & part-time developer (school years)

Gymnasium Gröbenzell · IT consultancy · Abitur 2004 · part-time web developer at an IT consultancy (2000–2002)

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Web applications and Linux administration, two years as a side job at an IT consultancy. Led the programming class for 5th graders as a 7th grader. Built a web platform for pupils with homework exchange, forum and calendar.

Web applications and Linux administration (side job at an IT consultancy, 2000–2002)
Taught a year of programming to the 5th grade (as a 7th grader) – made the lab computers Tcl/Tk-capable via floppy disks, wrote the teaching material himself
Own web platform for pupils: homework exchange, forum, calendar
class website in 10th grade with a forum written in Perl: accounts, sharing homework, chat
joined the software house after testing a medical association’s website before being hired and submitting pages of bug reports – then co-developed the doctor search with radius search and maps
Two years of elective rhetoric classes at school – presenting and explaining as an early-practised craft that runs through trainings, coaching and talks to this day
Built an online store and point-of-sale software for a pet-supplies shop (2002–2009, on the side): receipt printer, cash drawer, inventory, invoicing – published as open source “BLAX!” on SourceForge in 2006

Depth of expertise

What he builds with today

Foundation

Bars: self-assessment. Left: outcomes; right: years and stations computed from the career. Click to see the stations in the conversation – or add a technology or soft skill.

Projects

Things you can touch.

2024 – 2026

Edge controller on Raspberry Pi CM5

LED status display over SPI and speech output via ALSA on the care-IoT edge controller – from the Buildroot Linux down to the driver.

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2026

This website

RAG as a CV: the assistant retrieves its answers from the page content and operates the page itself – no framework, under 120 KB, built with Claude Code.

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2026

Clauboy

GitHub

First home-built multi-agent orchestrator: one Claude Code agent per GitHub issue in an isolated container, about 400 issues worked through. Since superseded.

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1997 – 1998

Programming lessons for a fifth-grade class

As a seventh grader, a year of teaching a fifth-grade class: computers brought to Tcl/Tk via floppy disk, teaching material written himself, a calculator as the final project – the school report recorded it.

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Smaller projects

2015

Audio analysis by waveform

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2012 – 2013

LED cube – wireless lighting system

Video (YouTube)

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2009 – 2010

Control interfaces for laser and medical devices

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2009

Website operations for a Munich fashion retailer

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2006

BLAX! and BlackVisi – open source

SourceForge

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2002 – 2009

Online shop and POS software for a pet-supplies store

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2000

Class website with its own forum

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Talks & streams

Still image served locally – the player loads only after you click.

**From slow to fast: Java optimisation to just below the speed of light**talk, Java User Group Munich, February 2026

**Why neither LocalDateTime nor long solves all your date-and-time problems**talk, Java User Group Munich, January 2025

**Coding and chatting**live-coding stream (TypeScript/React), YouTube channel bartfastiel

**Chatting while coding the online “Wusel” game**live-coding stream, YouTube channel bartfastiel

Availability

What he is looking for – and what not.

Role: AI Architect, Principal / Lead / Senior Engineer – preferably a small team with a real product, ideally IoT or close to hardware, that truly works together (pair programming, thinking things through jointly)
Hours: ideally 30 hours per week – more is negotiable
Location: fully remote; 1–2 on-site days per week – within easy reach from the Hallertau: Munich, Garching, Ingolstadt, Regensburg, Landshut, Augsburg
Model: permanent position preferred, freelance conceivable
Start: from 1 January 2027 – as a starting point for negotiation, earlier on request
Languages: German and English · German (native), English (fluent), French (B1)

Remote is the default. For one or two on-site days per week, much is within easy reach from the Hallertau – Munich, Garching, Ingolstadt, Regensburg, Landshut, Augsburg. Schematic drawing, no external map service.

A fit if …

a real product is at the centre – ideally IoT, robotics, energy, MedTech, embedded
a small team with real ownership wants to work AI-natively – and truly works together: pair programming, thinking things through jointly
architecture or lead responsibility with hands-on work is meant
remote with one or two on-site days per week works – Munich, Ingolstadt, Regensburg, Landshut, Augsburg are within easy reach

Not a fit if …

relocation is expected
more than two on-site days per week are mandatory
pure ML model building or data science is wanted
consulting without a product core or body leasing is meant
part-time is ruled out altogether

References

Verbatim from employment references, reference letters and LinkedIn recommendations – text versions on this page, originals on request.