Hi, I'm Holger Sielaff, a Freiburg-based software developer with more than two decades of professional experience. I freelance for clients worldwide, focusing on backend architectures, PHP, Python, and cloud-ready solutions. Over the years I've led development teams, managed IT operations, and built secure, scalable systems for sectors like healthcare, logistics, and education. I enjoy turning complex requirements into robust software, partnering with customers to deliver value, and maintaining an agile mindset. When I'm not coding, I manage projects and help teams improve processes, while keeping a hands-on technical edge in PHP, Django, Phalcon, WordPress, Odoo, and related technologies.

Holger Sielaff

Hi, I'm Holger Sielaff, a Freiburg-based software developer with more than two decades of professional experience. I freelance for clients worldwide, focusing on backend architectures, PHP, Python, and cloud-ready solutions. Over the years I've led development teams, managed IT operations, and built secure, scalable systems for sectors like healthcare, logistics, and education. I enjoy turning complex requirements into robust software, partnering with customers to deliver value, and maintaining an agile mindset. When I'm not coding, I manage projects and help teams improve processes, while keeping a hands-on technical edge in PHP, Django, Phalcon, WordPress, Odoo, and related technologies.

Available to hire

Hi, I’m Holger Sielaff, a Freiburg-based software developer with more than two decades of professional experience. I freelance for clients worldwide, focusing on backend architectures, PHP, Python, and cloud-ready solutions. Over the years I’ve led development teams, managed IT operations, and built secure, scalable systems for sectors like healthcare, logistics, and education.

I enjoy turning complex requirements into robust software, partnering with customers to deliver value, and maintaining an agile mindset. When I’m not coding, I manage projects and help teams improve processes, while keeping a hands-on technical edge in PHP, Django, Phalcon, WordPress, Odoo, and related technologies.

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Experience Level

Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
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Language

German
Fluent
French
Advanced
English
Advanced

Work Experience

Freelance Software Developer at Self-employed / Freelance
May 1, 2004 - October 28, 2025
Development of complex software projects; led development teams; web frontend/backend with PHP, Python, Django, WordPress, Odoo; IT management and client engagement.
Owner at Mensa3
July 1, 2016 - July 1, 2016
Owner of Mensa3; responsible for business operations and strategy.
Lead Developer, Project Manager, Head of IT at Billexco AG (Freelance)
June 1, 2013 - October 28, 2025
Development and implementation of new modules; test development Windows client; installation and operation of development/test instances; general SOAP web interface and microservices; debugging and updates; 1st-3rd level support; sysadmin.
Senior Software Architect, Head of IT at Brainson GmbH
February 1, 2018 - October 28, 2025
Backend architect & developer for a coin auction portal; development of homogeneous development environment (Proxmox containers); VPN structure and LDAP-based global authentication; Debian-packaged WordPress lifecycle; LDAP-based global authentication; Docker, Nginx, Phalcon, MySQL, Apache, git, Python, Django; project leadership and sysadmin.

Education

Abitur at German-French Gymnasium Freiburg / Berthold Gymnasium Freiburg
January 1, 1983 - January 1, 1992
Journeyman's certificate at Electrical Trades Apprenticeship
January 1, 1995 - January 1, 1998
Law – no degree at Albert-Ludwigs University of Freiburg
January 1, 1998 - January 1, 2004

Qualifications

Journeyman's certificate
January 1, 1995 - October 28, 2025

Industry Experience

Software & Internet, Education, Healthcare, Professional Services, Transportation & Logistics

Experience Level

Expert
Expert
Expert
Expert
Expert
Expert
Expert
Expert
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
See more