Software architecture and engineering
Architecture and hands-on development of TypeScript and Node.js systems: web applications, REST and OpenAPI services, OAuth and OIDC authentication, and standards-based frontends.
Open for new engagements
Software that has to work.
I am Jonatan Pedersen, an independent software consultant in Copenhagen. For 25 years I have built production systems in healthcare, public health, and fintech, including a class IIb medical device, the booking platform for Denmark’s COVID-19 vaccination programme, and accounting software used across Europe.
- 25 years
- in software engineering
- Class IIb
- medical device, certified
- 300,000+
- people vaccinated against COVID-19
- 10,000/s
- requests in a national booking queue
What I do
Senior engineering and leadership for systems where reliability matters.
Regulated and medical software
Development and certification of software under IEC 62304 and IEC 82304, including a class IIb medical device, with the design controls, risk management, and documentation that audits require.
Fractional CTO and engineering leadership
Technical leadership for engineering teams: setting architecture and direction, hiring and structuring teams, and establishing development and release practices, based on prior roles as CTO and engineering manager.
Platform and scale
Design of systems for high load and reliability, including a queue handling 10,000 requests per second and the infrastructure for a national vaccination programme.
AI
Practical adoption of AI tooling: identifying where it delivers measurable value and where established engineering practices remain more effective.
Selected work
Teams and products I have helped build.
Hedia
Principal engineer and engineering manager on a class IIb diabetes-management medical device.
Practio
Supported the vaccination of more than 300,000 people against COVID-19; designed a booking queue handling 10,000 requests per second.
Debitoor and SumUp
CTO of an invoicing and accounting product used by small businesses across Europe.
Yahoo! and Kelkoo
Product development and search ranking for a European shopping comparison service.
I am also building Virksomhed: apps for small businesses, starting with Konsulent for consultants’ clients, engagements, and hours.
How I work
Much of my work has been in domains where failure carries real consequences. I work with teams under regulatory constraints, scaling quickly, or facing problems that call for experienced engineering judgement.
Hands-on engineering
I work directly in the codebase, not only on diagrams and planning.
Long-term quality
Tests, type safety, and the maintenance discipline that keeps systems reliable for years.
High-stakes domains
Regulated, high-traffic, and safety-relevant systems where correctness is essential.
Proven at scale
A record of delivering large systems under real operational demands.
What people say
From colleagues, managers, and clients.
Jonatan has an amazing drive, he is a powerhouse of getting things done. Always looking for ways to improve infrastructure and tooling around the software we build at Debitoor. An awesome developer with passion. I nominated Jonatan for the best developer in Denmark-award, and he won second place. I promoted Jonatan to Team lead and he also excelled in this role. Is there anything this guy can't do? If you have the chance to work with Jonatan you should seize it, you will not regret it.
Jonatan is technically skilled, a great team player and extremely dedicated. When he sets a goal, he'll understand everything necessary to achieve it and keep pushing until it's done.
Jonatan he has always been able to comprehend and communicate both the user and commercial aspects of a project. Transforming an idea into something real and useful only seems like play to him. He is straight forward, honest, open minded and very pleasant to work with.
Let’s build something that works.
Email is the best way to reach me. Include a short description of your project and the support you need, and I will respond.