John Hamelink

Theo is a pre-revenue sports-tech company, building wearable tech devices aimed at pro-athletes who are training through recovery.

As Lead engineer at Theo, my responsibilities included re-implementation of the backend infrastructure, development and implementation of the core algorithm, working closely with a Mathematician and Biomechanist to deliver a high performance, concurrent and test-driven library in Rust, packaged into a C++ Turbomodule for use with React Native for iOS devices.

I wrote a multi-platform rust command-line application which collects stream data concurrently against multiple connected BLE devices and record their sensor data for analysis during a motion-capture study with Strathclyde University. I also maintained and improved the firmware of the core ESP-32 device, including implementing a high-performance encryption algorithm for the bluetooth stream. Managing a team of 2 engineers, as well as a Mathematician and Biomechanist, my role included day-to-day steering and coordinating of the team, including task allocation and general office management duties.

I reimplemented our entire backend infrastructure from scratch, moving from GCP to budget host Hetzner, reducing server costs by over 80% in the process. I built a fully automated CI/CD pipeline using self-hosted github actions, which allowed us to deploy our backend and react native codebases. I moved multiple external services to self-hosted variants, further reducing the business' subscription costs, and managed all of this complexity using Nix and NixOS in order to declaratively define our configurations in a way that can be reused across our stack and from within local dev environments. The result was a fully integrated solution for our business, which was also significantly cheaper to maintain, and built for scale.