Jens R.-Technical Product Owner
Check rate
Experience
Platform Architect & Senior Developer
Direct client, industrial measurement technology, medium-sized company
- Technical leadership across hardware, firmware, and software teams; scope: hardware/firmware team (4 people) and leadership group (5 people)
- Consolidated and documented a product family that had grown over more than 15 years and aligned it with CRA compliance — from the bare-metal I/O module to the cloud interface.
- Provided the most important customer product with the essential requirements and architecture documentation within two months — for a firmware landscape that had grown over more than 15 years. It now supports the customer’s modernization strategy.
- Established a monthly reporting line to the supervisory board and executive board within three months: nine meetings since 12/2025. The report itself is versioned and built from the CI pipeline; it is based on automatically collected activity and release data instead of assessments.
- Built a container-based CI/CD infrastructure from scratch: cross-compilation, host tests, and documentation builds in one continuous pipeline.
- Introduced declarative QA gates for DevOps and development artifacts — from the start using lefthook instead of pre-commit, executed in a dedicated container image.
Technologies used: arc42, req42, tpo42, docToolchain, PlantUML, ArchiMate, C4 model, ADR, C, C++ (GTest), CMake, Bare Metal (ARM Cortex-M3/M7), OCI containers, Jenkins, lefthook, Prometheus, Grafana, SBOM, CRA, OPC, SCADA, PLC integration, IPv6 migration, Zero Trust, Sociocracy 3.0, Cynefin
Technical Product Owner
App Development
Development of a mobile app to slow the progression of dementia
Coordination of software development (TPO – technical product owner)
Agile requirements management (agile requirements engineering)
Prioritization of tasks in consultation with stakeholders
Stakeholder management
Documentation and management of the software architecture
Conducting PoCs for technology decisions
Documentation as Code
docToolchain, arc42, req42, aim42, tpo42, C4 model, ArchiMate
ADR, Architecture Decision Records
Docker
Pre-Commit, Conventional Commits, Semantic Versioning
Liberating Structures, Agile Principles, holacracy, Sociocracy 3.0
Mobile frameworks
AI development interfaces, LLM
Cordova, Unity
Google Gemini, OpenAI, Character.AI
Prompt development
Framework Creator, Architect
Open Source, Methodology
- tpo42 — connected req42 and arc42 into one documentation model, canvas templates upstream at arc42
- Open-source framework that connects requirements (req42) and architecture documentation (arc42) in one model for Technical Product Owners — shared content is included in both documents from one source using tagged includes. Also ADCW, a Ruby-native AsciiDoc toolchain in a container with a continuous quality-gate chain. The arc42 project has adopted the LaTeX canvas templates in its official download section.
Technical Product Owner
Testing & Measurement Technology
Provision of the software platform for the new generation of inspection technology
Coordination of software development (TPO – technical product owner)
Agile requirements management (agile requirements engineering)
Prioritization of tasks in consultation with stakeholders
Stakeholder management
Documentation and management of the software architecture
Guidance for team self-organization (agile coaching)
Running agile ceremonies
Preparation and facilitation of retrospectives
Software supply chain management
Documentation as Code
docToolchain, arc42, req42, aim42, tpo42, C4 model, ArchiMate
ADR, Architecture Decision Records
Confluence, Jira, ConceptBoard
BitBucket, GitLab
Docker, Yocto, SDK
Pre-Commit, Conventional Commits, Semantic Versioning
Kanban, regular meetings, facilitation techniques
Liberating Structures, Agile Principles, holacracy, Sociocracy 3.0
Agile ceremonies (retrospectives, refinements, demonstrations)
QA metrics
SBOM, Software Bill of Materials
VISCA protocol
Jira management (administration)
Hardware architecture
TPO, Platform Architect & Senior Developer
Manufacturer of industrial testing and inspection technology
- Technical coordination across firmware, HAL, and hardware teams; 6 people in the development team
- Took responsibility for the software platform of a new camera generation from architecture through delivery — switching between design, hands-on development, and coordination depending on the current bottleneck.
- Delivered a software release that had remained unfinished for two years within six months.
- Reduced the development cycle for each new feature from eight weeks to three days — turning a linked library with deadlocks into a self-contained, reentrant service with barely measurable resource consumption.
- Kept control latency at around 10 ms round-trip and therefore far below the roughly 250 ms delay in the video path — even with 100 m cable length, camera control was never the limiting factor.
- Opened work on the second camera generation to four of six team members, although complete test hardware was available only to the hardware developer — using a three-stage test strategy comprising unit tests, software-in-the-loop, and integration tests.
- Documented architecture decisions as ADRs and structured decision-making with a Pugh matrix; management was involved in the process through agile ceremonies rather than a separate reporting meeting.
Technologies used: arc42, req42, tpo42, aim42, C4 model, ADR, Pugh matrix, C++23, Boost.Asio, Protobuf, Yocto, NXP i.MX6, Device Tree, OCI containers, GTest, PyTest, HiL, SiL, Jira, Confluence
CI/CD Platform Architect & Agile Coach
Energy industry, distributed product development across multiple locations, through an agency
- 6 developers in my own team, all working through the platform; designed for additional engineering teams across locations
- Replaced fully manual integration processes in hardware-in-the-loop testing with a continuous integration platform.
- Created an automated deployment path from the cloud pipeline to the internal documentation platform: no automated deliveries before, then with every release.
- Developed and documented the related overview during four months of data center debugging.
- Moved all six developers on the team to the platform; dependent teams adopted the approach afterward.
- Documented the architecture throughout using arc42 and established it as a living reference within the team.
Technologies used: GitHub Actions, GitHub Workflows, Docker, Podman, Azure Cloud, Jinja, arc42, C4 model, ADR, ArchiMate, docToolchain, Documentation as Code, Pre-Commit, Liberating Structures, Sociocracy 3.0
Senior Yocto Engineer & TPO
- Complete reference BSP with a custom update framework: signed deployment bundles, freely selectable slot layouts (A/B, A/B/C, provisioning, data and update partitions), factory provisioning; signed field update in 60 seconds, complete build from an empty tree in around 30 minutes.
- Supported the BSP across two processor architectures — TI Sitara / BeagleBone Black Industrial (ARM) and BeagleV-Ahead (RISC-V).
- Published and continuously maintained two layers.
- Documented throughout according to tpo42 (arc42 + req42).
Consultant / Design
Energy industry
- Stabilized the Yocto platform of a field-oriented gateway on NXP i.MX8: reduced boot time from two minutes to 40 seconds, analyzed the BSP and provided a list of changes that reduced the build time by 40 minutes in the first step.
- Switched backend communication fully to IPv6.
- Integrated test coverage measurement into the build.
Industry experience
See where this freelancer has spent most of their professional time.
Experienced in Manufacturing, Information Technology, Healthcare, and Energy.
Business area experience
See which departments and functions this freelancer has contributed to most.
Experienced in Information Technology, Quality Assurance, Product Development, and Project Management.
Summary
Jens Rehsack is a self-employed systems and platform architect with 35 years of professional experience, 30 of them full-time. His field of work is the interface between device and operations: About half of his career has been in embedded and IoT platforms, the other half in the data center, working on platform architecture, containerization, and operations. Both tracks have run in parallel since 1998, not one after the other — he has taken the same C library from 96-CPU machines down to microcontrollers with less than 32 MB of RAM and operated it there.
His approach to established system landscapes is an assessment of the current state: What is actually running, where does the documentation differ from reality, and which knowledge exists only in individual people’s heads. From this assessment, he creates arc42 architecture documentation, well-founded decisions (ADR), and a prioritized roadmap with effort estimates. At a measurement technology manufacturer, he used this approach to fully document a firmware landscape that had grown over more than 15 years for the first time; it now supports the company’s modernization strategy.
He sees architecture work as including the task of making it defensible to senior management. Since 12/2025, he has reported monthly to the supervisory board and executive board, changed the reporting format when the message no longer worked for the committee, based the report on automatically collected metrics instead of assessments — and also shows a declining maturity level, because the credibility of the figures depends on it. At an energy company, coordination with the CPO, CIO, and CISO resulted in binding architectural guardrails for around 20 development teams across three companies in the group.
He is the creator of the open-source framework tpo42, which connects req42 and arc42 in one documentation model; arc42 has adopted the associated canvas templates in its official download section. Also publicly verifiable: NetBSD committer since 2008 with 4,659 commits to pkgsrc across nine operating systems, core developer of libstatgrab, 75 upstream commits to Yocto/OpenEmbedded, and five merged pull requests for docToolchain.
Skills
Architecture & Methodology
- Arc42, C4 Model, Archimate, Adr (Architecture Decision Records)
- Req42, Aim42, Tpo42 — Requirements And Improvement Side
- Documentation As Code (Doctoolchain, Asciidoctor, Asciidoc)
- Uml, Sysml, Plantuml, Ooa/Ood (Booch, Omt), Design Patterns
- Interface Descriptions Based On The Osi Layer Model In Arc42 Building-Block Views
- Architecture Assessment, Architecture Review, Technology Evaluation, Feasibility Analysis, Modernization Roadmap, Effort Estimation
- Scenario-Based Architecture Evaluation: Atam (Architecture Tradeoff Analysis Method) And Quality Attribute Scenario
- Modeling And Diagrams: Sparx Enterprise Architect, Draw.Io / Diagrams.Net, Plantuml As Diagram Source Code, Archimate, Visio, Conceptboard
- Application Lifecycle Management (Alm): Polarion, Doors, Jira, Confluence
- Architecture Governance: Architecture Board, Guardrails, Communities Of Practice, Raci Role Models, Metrics For A Professional Career Path
Platform, Cloud & Operations
- Containers & Orchestration: Kubernetes, Talos Linux, Helm, Kustomize, Argocd, Gitops, Docker, Podman, Toolbx, Cilium (Ebpf), Software Defined Storage With Rook-Ceph/Cephfs, Cloud Native Computing Foundation
- Ci/Cd & Automation: Gitlab Ci, Github Actions, Jenkins, Infrastructure As Code, Configuration As Code, Pipeline As Code, Cfengine, Ansible, Sops/Age, Pre-Commit, Lefthook
- Operations: Operating Concepts, Disaster Recovery, High Availability (Hacmp, Etcd Quorum, Failure Domains), Cmdb, Itil, On-Call Duty, Capacity And Cost Transparency
- Observability: Prometheus, Grafana, Nagios/Icinga, Snmp (Snmpv3 Server In C++, Mib Design), Libstatgrab, Collectd, Rrdtool, Influxdb, Timescale, Sli/Slo/Sla, Counter Semantics, Self-Monitoring
Operating Systems
- Linux & Container Os: Rhel, Sles, Debian, Ubuntu, Centos, Talos Linux; Kernel Development (Arm, Firewire), Kernel Configuration, Driver Maintenance
- Unix: Aix (Extensive, Lpar/Wpar/Hacmp), Solaris 5.6–11 (Zones), Hp-Ux, Freebsd, Netbsd, Openbsd, Macos
- Embedded / Real-Time: Yocto Project / Openembedded (Bitbake), Embedded Linux, Board Support Package, Device Tree, Bare Metal / Main Loop, Vxworks, Freertos, Zephyr (Poc), Posix Real-Time Extensions
- Legacy (Reliable During Incidents): Irix, Tru64/Dec Osf/1, Ultrix, Vms, Os/2, Mvs/Z-Os Integration
Networking, Security & Regulation
- Tcp/Ip (Ipv4, Ipv6, Dual Stack, Dhcpv6), Ipsec, Vpn (Openvpn, Wireguard), Snmp
- Ddi — Dns, Dhcp, And Ip Address Management (Ipam) As One Connected Discipline; Address Planning For Entire Development Areas
- Network Segmentation: Vlan (Single-/Double-Tagged), Software Defined Network, Zone Concepts, Air-Gapped Operations
- Pki: X.509/Asn.1-Der, Cluster-Internal Cas, Trust Chains, Certificate Lifecycle (Acme/Step-Ca/Vault), Mtls, Device Identity
- Zero Trust, Selinux Hardening, It Baseline Protection, Identity & Access Management (Kerberos, Ldap/Ad, Sso), Secret Management
- Software Bill Of Materials (Sbom), Software Supply Chain, Vulnerability And Patch Management
- Cra, Nis2, Data Act, Red Art. 3.3, Product Liability
- En 18031, Iec 62443, Tara And Design-Fmea
- Messaging: Mqtt, Kafka, D-Bus
- Industrial Protocols: Opc Ua, Modbus, Profinet, Industrial Ethernet, Can, Scada/Plc Integration, Iec 61131-3, Iec 61499
- Industry 4.0 / Iiot
Agile Methods & Facilitation
- Scrum, Kanban, Safe, Spotify Model (Communities Of Practice / Guilds)
- Liberating Structures, Holacracy, Sociocracy 3.0 (Consent, Objection)
- Cynefin As An Argumentation Framework, Pugh Matrix As A Decision Framework
- Retrospectives, Refinements, Facilitation Techniques, Pair And Crowd Programming
- Product Vision, Use Cases, User Stories, Epics, Backlog Prioritization, Acceptance Criteria, Definition Of Ready And Definition Of Done, Mvp
Embedded Linux & Device Platforms
- Yocto Project, Openembedded, Bitbake — Upstream Contributor With 75 Merged Commits, Own Layers And Recipes
- Board Support Package (Bsp), Device Tree, U-Boot, Tf-A/Atf, Cross-Compile Sdk, Read-Only Rootfs
- Nxp I.Mx6, Nxp I.Mx8, Ti Sitara, Beaglebone, Marvell Kirkwood, Arm, Risc-V, Freertos, Bare Metal
- Secure Boot, Signed Updates, A/B Update Strategies, Sbom, Update Framework For Device Fleets
- Cyber Resilience Act (Cra), Iec 62304, Product Safety For Connected Products
Framework
- Service Contract Only, No Employee Leasing
- Primarily Remote From The Rhineland, On-Site Appointments By Agreement
- Two Completed Security Clearances, Most Recently An Enhanced Ü2 Clearance In The Defense Sector; Both Authorizations Have Expired, Renewal Possible
Languages
Education
Martin Luther University Halle-Wittenberg
Computer Science · Halle (Saale), Germany
Georg Cantor Grammar School
Abitur · Mathematics, Natural Sciences & Technology · Halle (Saale), Germany
Specialized in Mathematics, Natural Sciences & Technology
Certifications & licenses
Polarion Basic Training & Advanced Training
PostgreSQL Administration
Samba
VxWorks 6.3 & WindRiver Workbench 2.5
TFC Training Level 1
Statistics
Experience
Global experience
Expertise
Qualifications
Profile
Frequently asked questions
Have questions? Find more information here.
Jens is based in Kerpen, Germany and can operate in on-site, hybrid, and remote work models.
Jens speaks the following languages: German (Native), English (Advanced), Russian (Intermediate), Latin (Elementary).
Jens has at least 3 years of experience. During this time, Jens has worked in at least 7 different roles and for 7 different companies. The average length of individual experience is 5 months. Note that Jens may not have shared all experience and actually has more experience.
Based on recent experience, Jens would be well-suited for roles such as: Platform Architect & Senior Developer, Technical Product Owner, Framework Creator, Architect.
Jens's most recent position is Platform Architect & Senior Developer at Direct client, industrial measurement technology, medium-sized company.
In recent years, Jens has worked for Direct client, industrial measurement technology, medium-sized company, App Development, Open Source, Methodology, Testing & Measurement Technology, and Manufacturer of industrial testing and inspection technology.
Jens is most experienced in industries like Information Technology, Manufacturing, and Energy. Jens also has some experience in Healthcare.
Jens is most experienced in business areas like Information Technology, Quality Assurance, and Product Development. Jens also has some experience in Project Management.
Jens attended Martin Luther University Halle-Wittenberg for Computer Science.
Jens has 6 certificates. Among them, these include: Polarion Basic Training & Advanced Training, PostgreSQL Administration, and ITIL Processes.
Jens is immediately available full-time for suitable projects.
Daily rate distribution
The rates shown represent the typical market range for freelancers in this position based on recent contracts on our platform.
Average rates for similar positions
Rates are based on recent contracts and do not include FRATCH margin.
The average daily rate is the mean of all daily rates from recent contracts of comparable freelancers on our platform.
The median daily rate is the middle value of all daily rates — half of comparable freelancers charge less, half charge more. Unlike the average, it is barely affected by outliers.
Calculated based on our freelancers’ daily rates as of 27 Sep 2026. Actual rates may vary depending on seniority level, experience, skill specialization, project complexity, and engagement length.
Similar freelancers
Discover other experts with similar qualifications and experience
Ulf S.
Laurin H.
André H.
Wolfgang D.
Frédéric K.
Kiriakos K.
Jozsef F.
Tungi D.
Sebastian S.
Matthias K.
Experts recently working on similar projects
Freelancers with hands-on experience in comparable project as a Platform Architect & Senior Developer
Gavrilo O.
Volker F.
Andre K.
Burhan D.
Arne H.
Peter K.
Ornel Franck W.
Waldemar B.
Konstantin M.
Jürgen F.
Nearby freelancers
Professionals working in or nearby Kerpen, Germany
Wilhelm K.
Thorsten H.
Artur S.
Eberhart N.
Andreas S.
Matthias S.
Rafael D.
Amit S.
Marc H.
Luisa J.
