Senior Principal Software Engineer Sweden
I’m Thomas Hallgren. I design and build software where languages, networks, developer tools, and distributed systems meet. Today I work at Polar Sky on the foundations for secure, trustworthy enterprise AI.
For more than four decades, I have been turning difficult, cross-layer problems into systems other engineers can understand, operate, and extend.
01 / Now
The current work is new, but the questions beneath it — around identity, data, protocols, failure modes, and developer experience — have followed me through much of my career.
Senior Principal Software Engineer
Building systems that help enterprises understand and control data exposure and security risk as they adopt AI. In a small team, architecture and implementation remain inseparable — exactly where I do my best work.
Visit Polar SkyLead developer and maintainer
Alongside my full-time role, I continue to guide the architecture, releases, security, and long-term maintenance of Telepresence OSS.
02 / Selected work
The technologies have changed. The recurring work has not: make complex systems more coherent, dependable, and useful to the engineers who rely on them.
Original creator
I created PL/Java, an open-source PostgreSQL extension that lets developers write stored procedures, functions, and triggers in Java.
Project wikiFounder and chief architect
At Cloudsmith Inc., we built a model-driven tool for describing software architectures and deploying them into cloud environments. The work grew out of our experience with Eclipse-based component assembly and automation.
Related Eclipse projectSoftware architect and developer
I worked on JRockit, BEA’s high-performance Java virtual machine, contributing to the runtime and the engineering around a production JVM used in demanding server environments.
Software architect and developer
I worked on core parts of the Puppet language compiler and data type system: parsing, evaluation, object types, loaders, serialization, performance, and the specifications that kept the pieces aligned.
Puppet sourceLead developer and maintainer
I work across its full architecture: cluster networking, workstation integration, Kubernetes controllers, protocols, security, release engineering, documentation, and the small details that make a developer tool trustworthy.
Source and releasesSoftware architect and developer
Working on-site with a Manhattan-based startup, we developed a framework that took a UML 2 model as input and used it to run a complete layered enterprise application model.
Software architect and developer
We created Xancus, our own virtual machine for an object-oriented language similar to Python. I was instrumental in implementing its persistent storage and database layer, together with the incremental garbage collector.
03 / Career thread
Selected chapters that explain how the current work came to be.
04 / Open source
I welcome thoughtful technical discussion, bug reports, design ideas, and contributions around Telepresence. Organizations that depend on the project can also support its continued maintenance directly.